Phone plans?

Hey all,

I'm moving to Edinburgh beginning of June under a Youth Mobility visa for 2 years, and I was wondering about phone plans. Since I don't have any credit there, what are the rules for getting a phone contract? I heard you can also get a month-to-month plan, where you buy the phone separately, buy a SIM card and pay each month, but you can stop it at any time. I don't want to be paying as you go, as I like having a plan but I'm still not sure what my limitations are.

Thanks for your help!