Hi all
firstly I apologise if this question is on the wrong forum.

I'm in the UK and currently have a Samsung F480 on an O2 contract with nearly 12 months left to run. It's a £35 per month reduced to £25 through a Carphone Warehouse loyalty screen - I get 600mins 1000 texts and 200mbs web browsing (not sure exactly what the latter is).

Anyway I'm thinking of buying a second-hand 3G 8mb iphone and using the sim from my current phone/conract in it. I asked about doing this via a purchase from Carphone Warehouse but they said that my sim wouldn't allow all of the iphone facilities. A very quick look on the net suggested that I wouldn't get video messaging and that don't bother me!

Can I do it with my sim and contract? What will I miss out on? Do I need an unlocked iphone given that mine is an O2 contact?

Help help help please. All comments will be greatly appreciated.