Spending 6 months in the UK, help me figure out my phone options?

[jimmyrules712]

I'm going to be in the UK this year from october through next february and I will have a 3G iphone with me.

Assume I get the phone unlocked before I leave and thus can use it with any GSM sim.

I'm considering paying for a data plan if it is possible but I'm having toruble figuring out what's out there, etc.

So any UK experts please advise.