Richy,
As I understand it (and I am no expert) a degree is not an entry requirement for airlines such as BA- it tends to be 5 GCSE's A-C in academic subjects and 2 A/AS Levels. Having said that, a degree is preferred- it doesn't matter too much what subject, but it shows that you have the will power and the academic strength to study intensively under your own steam and get the results at the end of the 2/3 years or whatever. Technically airlines would accept you without a degree, but it would improve your chances and improve the impression you make with the airline if you have a degree under your belt to accompany your other achievements.
As to what chances you would have of getting sponsorship (where the airline pay for all of or part of your training on the condition that you remain with the airline for a certain period) without a degree would be, I'm not too sure.
Try doing a search of Wannabes for this sort of thing, there have been loads of similar subjects and questions asked to this one.
Good luck,
Landing_24R
