As reported by Simon on the front page, after investigating flights to Sweden I've found you can get there for as little as £17.98 with Ryanair. If you go to the Ryanair website and search for flights from Gatwick to Stockholm, it's only £8.99 there on the 9th, 10th and 11th (Wed-Fri) and £8.99 back on the 14th, 15th and 16th (Mon-Wed). Of course being Ryanair there are added fees if you want to take checked baggage and admin fees if you don't have a prepaid credit card, but even in that instance it's £60 which isn't bad.

If you don't have a prepaid card, I'd recommend either FairFX or CaxtonFX, they're exceptionally useful when a) booking with Ryanair and b) travelling abroad, as you don't get charged for overseas withdrawls.