Welcome back to PCMag's Fastest ISPs. We're continuing to investigate the upload and download speeds of the Internet service providers (ISPs) in foreign countries, moving now to the United Kingdom of Great Britain and Northern Ireland.

Here in the U.K., broadband speeds are regulated by the Office of Communications (Ofcom), a government watchdog. In 2007, the group suggested that more than half of the country was equipped with broadband, running average speeds of 4.6 Megabits per second (Mbps).

What a difference six years make: In 2013, Ofcom reported speeds as high as 17.8 Mbps; it also counted an impressive 77 percent of U.K. adults with fixed and mobile broadband in the first quarter of 2014.

Still, Britons are not thrilled with their service: Complaints about mobile and broadband providers rose by 20 percent in the U.K. last year, reaching a whopping 19,288 grievances, according to industry website Cable.co.uk. The most common gripes are related to network service, contract issues, and customer service.

Curious about your own broadband Internet speed? Test it right now!

But perpetually gray skies are gonna clear up, if the U.K. government has anything to do with it. A new national ambition aims to bring ultrafast broadband of at least 100 Mbps to nearly all homes in the country, Cable.co.uk reported.

But the question remains: As major players like BT, Virgin Media, TalkTalk, and Sky duke it out over customer attention, which company actually provides the fastest service in all the land? Read on to find out.

To measure Internet speed, we work with our sister company, Ookla, the creator of Speedtest.net, the globe's most popular broadband testing service. The throughput ratings here are based on tests run at Speedtest.net by millions of unique users who provided their upload and download speeds.

We then generate for each ISP a PCMag Internet Speed Index rating—a weighted score calculated by taking 80 percent of the download speed and 20 percent of upload speed. That number helps us to quickly quantify the fastest Internet service providers.

Fastest ISPs in the U.K.

Fastest ISPs in the U.K.

Whether you're new to the area and want to hook up your cable in time for the next Game of Thrones series, or just want a change from poor customer service and continued blackouts—check out our list of the top 10 major ISPs in the U.K.

The data below highlights overall PCMag Speed Index scores—as well as indicators of download and upload speed the index is based on—for the 10 biggest providers in the country. More specifically, those with the biggest reach, capable of bringing service to almost any market.

Fastest ISPs 2015- United Kingdom

(Note that the fastest localized ISP, Broadband for the Rural North, has an unmatched PCMag Speed Index score of 359—maybe the best we've seen in any country. But, since it is currently available only in a select few areas of—you guessed it—the rural north of Britain, we can't count it as a "major" option.)

So, for the second year in a row, Virgin Media takes the crown. The super-group of U.K. broadband companies, Virgin Media was formed a decade ago from a number of mergers; the final outcome is a titan of TV, mobile, landline, and the Web. Operating on a level all its own among the major ISPs, the company boasts a 43.1 Speed Index across the U.K.—almost double that of the No. 2 provider, KC, which scored 22.9.

With the most extensive fiber-optic network in the country, Virgin easily leads the pack, boosting its Index Score by nine points from last year's 34.1. Download speeds also increased from 41.3 Mbps to 52.2 Mbps; as did upload speeds, growing from 4.9 Mbps to 6.6 Mbps.

Virgin offers bundled tiers of service: 50 Mbps download speed for £28.50 per month, 100 Mbps for £33.50, and 152 Mbps for £41; all prices are discounted for the first year. Even a few extra quid down the line could be worth it; don't expect 152 Mbps downloads from any other major ISP in the U.K.

The company's extensive network is about to get even bigger: In February, Virgin announced an additional £3 billion to raise speeds and increase service speeds by 33 percent in five years.

That's five more years for the competition to step up its game. Filling out the top five are KC, BT, Zen Internet, and PlusNet Technologies. Interestingly, BT (the Internet arm of the titan formerly known as British Telecom), Zen Internet, and PlusNet scored the top 10 ISPs' highest upload speeds—7.9, 7.6, and 7.0 Mbps, respectively. But still they couldn't manage to reach elite PCMag Speed Index levels.

In fact, it was the same top five as last year; all saw gains in their Speed Index, but landed in a different order. Zen moved from second to fourth place, while PlusNet dropped from third to fifth; KC and BT both shot up in the ranks. But all still have a rating about half that of Virgin Media.

Fastest ISPs in U.K. Cities

Fastest ISPs in U.K. Cities

Most folks don't worry much about neighboring cities' broadband speeds. They're more concerned about how quickly their family photos will upload to the cloud, or how fast One Direction's latest album is downloading from iTunes.

If you've been itching for a change of scenery, call your realtor: Lancaster's inconceivable download and upload speeds of 117.8 Mbps and 100.7 Mbps, respectively, gives the city an astonishingly high PCMag Speed Index of 114.4. This is thanks, no doubt, to the presence there of the aforementioned Broadband for the Rural North.

Fastest ISPs 2015- Cities with Fastest Broadband

The next fastest U.K. city, Scotland's Motherwell, has a 54.9 Speed Index, which is more in line with fellow Scottish Speed Index mates Bellshill (50.7) and Johnstone (50.3). In fact, Bonnie Scotland fared well among the top 10. Of the cities with the fastest broadband, only Lancaster, Keele, and Dunstable represent England proper.

Zooming out a bit, let's take a look at the biggest cities in the United Kingdom, and the major ISPs in each one.

London
The capital city of London is home to 8.3 million people, all of whom are undoubtedly clamoring to beat their friends at Candy Crush Saga or post selfies on Twitter. Perhaps setting the precedent for the rest of the country, the city is run by Virgin Media broadband—the fastest ISP in all metropolitan areas.

Fastest ISPs 2015-London, England

In foggy London Town especially, the company reaches impressive download and upload speeds around 43.6 Mbps and 6.3 Mbps; its 36.2 PCMag Speed Index also marks a huge leap from last year's 30.1. And that's actually the slowest Virgin runs in any major U.K. city (except Belfast).

Rounding out the top five are Ask4 Limited (a student-oriented ISP) with a score of 22.9, just ahead of BT (21.9), and Zen Internet (21.0) and PlusNet Technologies (19.2).

Birmingham
Making our way northwest, we reach the second most populous British city, Birmingham, where people visit the world's biggest Cadbury shop, and surf the Web on Virgin Media's 53.6 Mbps download speeds.

Eons ahead of BT's 23.9 Mbps and Ask4's 18.7 Mbps speeds, Virgin beat its own 2014 score of 33.9, tipping the scales this year at 44.1.

Fastest ISPs 2015-Birmingham, England

Manchester
Continuing up the M6, we reach Manchester, where folks are streaming Manchester United football matches over Virgin's impressive 53.4 Mbps download speeds, beating last year's rate of 43.4 Mbps. What's more, its 44.3 Speed Index score crushes second-best Zen Internet's 26.8.

Fastest ISPs 2015-Manchester, England

Leeds
Take a right turn and you'll end up in Leeds, where Virgin Media's competition boasts speeds half as fast. BT lands at a 23.2 Speed Index, compared to Virgin's 42.3; Ask 4, TalkTalk, and Sky all manage download speeds between 16 and 27 Mbps.

Fastest ISPs 2015 - Leeds England

Southampton
The last of England's largest and most populous cities is, as its name suggests, the very southern Southampton, whose residents unsurprisingly favor Virgin Media. The seaside locale, however, has some competition from BT. Still almost 25 Mbps slower than the No. 1 provider, BT claims a higher upload speed, and far surpasses the rest of the crowd.

Fastest ISPs 2015-Southampton, England

Cardiff, Wales
The Welsh capital of Cardiff also counts on Virgin Media, but leans heavily on Cogent Communications as a crutch. Cogent slides into second place, with a 35.0 Speed Index—almost equidistant between Virgin's 46.8 and BT's 23.0.

Fastest ISPs 2015 - Cardiff Wales

Glasgow, Scotland
Venture north of the border to the beautifully industrial city of Glasgow, and you'll find neon-orange soft drinks, deep-fried Mars bars, and happy Virgin Media customers. Probably some of the most satisfied ones, at that: Scotland's largest city exhibits 60 Mbps download speeds, propelling Virgin Media to the highest PCMag Speed Index score (49.7) among all the municipalities.

Fastest ISPs 2015-Glasgow, Scotland

Belfast, Northern Ireland
Across the Irish Sea, Belfast's proud history includes the building of the Titanic (maybe not so proud) and Liam Neeson's first acting gig. However, it is now home to rather lackluster Internet speeds, with scores ranging from 10.8 (Sky) to 29.2 (Virgin Media). Everyone's favorite ISP even took a dive in the past year, dropping from a 32.2 Speed Index in 2014.

Belfast, Northern Ireland

Conclusions

There's no question: Virgin Media leads Britain's major providers in every major municipality, as well as the country overall. The only way to beat it is to find your way with a local fibre provider, which are few and far between.

The nationwide runner up for speed, KC, doesn't make a showing at the municipal level, never getting enough tests within the cities themselves. But if you're looking for a non-Virgin provider and can't get KC, you probably should consider BT. It was third for the nation, but also placed at least second or third with every single municipality we drilled in on.