Graham,
Yep, I agree this could get very expensive. The only solution I can suggest is to wait until the last minute to try and find a last minute cheapy one way flight back to the U.K. I once had to do this, with nerves of steel I waited until the day before I left for Corfu and bought a last minute return ticket, but only used the return leg. That was 2 years ago and cost me £54!
A few days before you leave you might... with a little luck... find a cheap Corfu-U.K or perhaps even do it the way I did by purchasing a return ticket.
Thomsonfly/Flythomascook/Easyjet (no last minute cheapies tho')/all do one way to the U.K.
Or, you could leave it to the very last minute and give Sue a ring at Castaway Travel in Acharavi. Sue has access to all the flights coming to the U.K, even XL who do not sell Corfu-UK online over here. Sue is brilliant, a great help and if anyone can get you a return seat it will be her!
http://www.corfucastaway.com/Finding somewhere to stay should not be too difficult unless you are looking for a 2 bedroom apartment which there are fewer of.
Good luck,
Eileen.