Ring them up and tell them that, there is nothing a network can do about poor coverage. Tell them you've been a big fan of oragne but its no longer working out between you two. Tell the an amicable break up is the best way to go. hehe
They're all twats mate.
I'd ring them up, be polite, and talk it out with them, come to some sort of arrangement that works for both of you.
Tell them you're moving back to a city in about 12 months and you'd hate to leave on bad terms as you'd like to maybe come back to them in future. I'm sure you can get sommat sorted. If you just don't pay, they will pass the debt onto a debt collection agency and it will do you no favours.
you are really out of luck.
A couple of months ago orange tried changing its Terms of Contract to increase it's call costs and that was everyones chance to cancel their contracts without having to pay which 1000s of people did. Because of this Orange have now retracted the change and by doing so means that no one can now get out of their contract and are stuck with their 12/18/24 month contracts.
Usually if you are in the last three months of your contract, you can go to Carphone Warehouse or Phones4U and they will sometimes pay off your left over contract to help get you on a deal with them.