EE has massively bumped up prices of their contracts in the last year,and Vodaphone is not much better. They have rebranded it as "4G" but most of the country has no 4G access and yet prices have doubled(or even more),and service has gotten worse. I am with EE and where I live in Kent,it really looks like they have been shutting down towers or not bothering to repair ones which have gone down for weeks.
Essentially it is 3 that is the only company that can keep prices in check and EE and Vodaphone,even though they use some of the EE infrastructure - but since they are part of Hutchison Whampoa,I don't really think they want to play too many games with them!