There are ways to get out of contracts, idk how different things are in the UK.
Some kick you out of the contract if you use a forget ton of roaming minutes. You could always say you're enlisted in the military and getting deployed. They will ask for a document stating that you are, but you could type up one and literally sharpie over every word on the paper deeming it "classified" and they should legally still accept it. You can come up with something about you moving (but make sure you are "moving" to somewhere where they do not provide service at all, might require a proof of address though).
If you are willing to put up a fight, I'm sure there are plenty of ways you can escape your contract by arguing with customer service, speaking to managers, tell them that there is a change in their terms of service for the contract (there has to really be one, just look at recent updates) and inform them that you think it's unfair and wish to cancel. This will probably be a painstakingly long thing to do and you'll spend lots of time on the phone and on hold, but it might work.
None of these are 100% obviously but I'm going off word of friends, family, acquaintances, and popular internet postings.
