Hi Jambo, have a look at Steve Howard's site (shwoodwind.co.uk, sorry I can't do the link thing), he has plenty of hints and tips on how to do more minor repair work if you want to take a DIY sort of approach to maintenance if all you want to do is look after your own horns. There's also a lot of useful stuff in the Breakfast Room, look around for posts from Griff.
I have done quite a lot of minor work like leak fixing, replacing corks, regulating, lubricating and adjusting spring tension etc from reading no more than what I have mentioned above and a bit of experimenting. I'm one of those people who isn't afraid to get in there and tinker, that's why I like my job too!
The main things to remember are to try and take it gently and logically; adjusting one thing can have an effect elsewhere. Also, if you are adjusting, say, a screw of some type, remember its original position in case things start to get more rather than less out of whack.
Cheers, Bob
p.s. you are in Oxford? If you use Allegro Music, matey in there may help