Mobile operators in UK

EE

It is the largest mobile network operator in the UK, with around 28 million customers.
Virgin Mobile UK along with ASDA Mobile operates on the EE network under a MVNO agreement.
http://en.wikipedia.org/wiki/EE_(telecommunications_company)

Voda phone

The world's second-largest mobile phone company. As of March 2012, Vodafone UK has 19.2 million subscribers and is the third largest mobile telecommunications network nationally after EE and O2.
http://en.wikipedia.org/wiki/Vodafone_UK

02

It is the second-largest mobile telecommunications provider in the United Kingdom (after EE).
http://en.wikipedia.org/wiki/O2_(United_Kingdom)

Three
http://en.wikipedia.org/wiki/Hutchison_3G#United_Kingdom
http://en.wikipedia.org/wiki/List_of_United_Kingdom_mobile_virtual_network_operators

http://www.independent.co.uk/life-style/gadgets-and-tech/ee-crowned-uks-best-mobile-operator--vodafone-in-last-place-9189018.html
Britain operates on a GSM network.

http://ukmobilecoverage.co.uk/

Britain's largest mobile operator, EE, said on Monday it posted its best quarterly take-up of its 4G network in the first three months of 2014 due to growing demand for fast mobile Internet and forecast customer numbers more than doubling in 2014.

EE, a joint venture between Orange and Deutsche Telekom, said it added another 889,000 customers in the three months to March 31, taking its customer base to 2.9 million with nearly 5,100 corporate clients.

EE, formerly known as Everything Everywhere, said it was on target to exceed 6 million 4G customers by the end of 2014.

Despite the growth, the company said turnover during the quarter dropped 3.6 percent from a year ago to 1.6 billion pounds ($2.7 billion).

Operating revenue was down 1.7 percent on a year ago to 1.5 billion pounds which included the impact of regulatory cuts.

http://uk.reuters.com/article/2014/04/28/ee-results-idUKL6N0NK1RX20140428