In my short time here, I've seen this question asked loads.
The only way I can think of at the moment is to modificate it with a chip, which is not allowed as potentially Nintendo might be able to brick it (stop it from working) with an update they might release. So I wouldn't try that.
Didn't Microsoft stop some chips in the 360?
Try and buy some games from American online stores which ship to the UK or buy some American games off eBay.