At the moment there isnt a company you can simply hire to act as the middleman between you and kickstarter. There have been attempts in the past to make this work. But so far kickstarter and amazon (in the US) or their payment provider (UK) have squashed any attempts to do this.
So the only way to do it at the moment is to become a registered UK company with a UK bank account or become a register US company with a US bank account. If you do these things then you can create an account on Kickstarter to act as if you are a UK or US company.
Before Kickstarter came to the UK I considered doing this but the cost, even if you do it yourself is easily above the �2000 mark.
As Blinx123 said the typical way people get on kickstarter from other countries is by having friends or families who reside in the UK and they trust them to setup their account for them.
However a few people have run campaigns doing this and said it has caused problems, because you have to be able to completely trust the person whose account you used. E.g. if you setup a game and it raised (unlikely) �1 million, could you trust your friend to give you all the money.
If they didnt give you the money you would have no legal way to force them. And your reputation would get trashed with the potential bad publicity. Anyway just a thing to think about if you go the friend route.