Mobile Phone options for 6 months in UK

I wonder if anyone could be of help please.

I will be moving from Dublin to work in London for 6 months and was wondering what is the best thing to do regarding my mobile.

Roaming charges will be high if I use my existing iPhone over there (I'm with O2).

Is my best option to get another phone over there, with one of the UK providers?

You could just get an O2 payg sim over there and use your existing handset?

Thanks for the advice, I'll look into getting an O2 pay as you go SIM.

I am out of contract with O2 as I've had the phone more than 18 months, so I wouldn't have a penalty for leaving them.

Great, thanks for all the help.

has a good mobile comparison tab where you can check out all the deals.
Three used to offer a Like Home option where you can use your home minutes but for convenience I'd go for a UK sim and use Skype to call home.