Your BA should qualify you for a master's program. A master's on international fees seems to generally start at around the £7,000 price range depending on the school. University of Glasgow is costing me £9,800.
It is a lot, especially compared to what the home fees are, but my taught masters program is going to be an intense 12 months straight through and then I'm done. So depending on the degree you go for and the school you go to, it's entirely possible that would only have to pay that amount once. The tuition itself is cheaper than any school I looked into in the US, especially since those were all 2 year degrees. Then again, you do have the option to wait the 3 years until you qualify for the home fees so that's always a possibility too.
I would say look around at some of the websites of the schools you might be interested in and maybe send a few e-mails to them with any questions you have. You probably won't be able to start anything until Fall 2010 as most schools don't allow anyone to start in the Spring, so you have some time to sort it all out and see what your options are.