What are your requirements? I'd suggest grabbing a pre-paid SIM from each of the major networks and see which gives you the best signal and speeds in the locations you frequent, but this may seem excessive to most.

I signed up to a 2 year 5G deal with EE shortly before moving out of London, now the signal and speed are junk and I'm stuck in a 2 year deal.

Given the absurd amount our "contracted" price increases by each year (my monthly payment went up ~15% on a SIM-only plan thanks to RPI or whatever excuse they use) I'd be tempted to go with someone like GiffGaff or similar next (they're an MVNO on O2 network) and just get monthly goody bags, then you can ditch them the minute you've had enough and want to get better service/signal/data etc.