Now that I have the iPhone 3G, I'm selling my original iPhone but if I unlock it will it work on any UK network for pay as you go?
Also would I need to replace the network image at the top left hand corner from O2 to whatever network they would be on or does that change on its own?

If anybody could please answer this today or tomorrow please?
Just that I'm in a rush to sell it because I urgently need the money.

Many Thanks.