4 pre-interview rejectionsss yayy, me too. And same UKCAT score...
And now for your questions:
1) You can apply while you're on a course, but you need to check that the universities you apply to are happy for you to do that. Some places don't want dropouts from any course, for obvious reasons. Dmz was going to do this, so ask him
2) I don't know about the BMAT (the chance of failing and ending up losing a choice scared me off it) but I'd say make sure you seriously consider where the weaknesses of your application were before. You say you think that your PS was rubbish, but what do the universities say about it? Obviously it won't have been your grades, but Leeds give good feedback on their scoring system. For example, I know that I don't need more voluntary work, but I need to demonstrate a bit more passion about the course for next year. Make sure you find out about that. I don't know if there are people who have been accepted as reapplicants to Oxbridge, but I'm sure there are. I guess its probaly kind of rare, because once you've been through the cycle once, you just want a place anywhere. I wouldn't even consider Oxbridge if it was me, just because I don't want to waste a choice - I just want to go and study medicine. You have better grades than me though, so you probably could do it, if you improved your PS. Its a personal choice, but basically you need to make sure you know WHY they rejected you.
3) I'm sure if you apply to enough places you'll get a job - so far I've applied to maybe 7 HCA jobs, and heard only one thing back - and its not even an interview yet. And I've applied to a couple of jobs as a waitress/bartender. There are jobs out there - you just need to make sure you big up your voluntary work/work experience. Find ANYTHING relevant to the job you're applying for in your work experience etc. And look for posts that don't ask for experience. Failing that, get more voluntary work - at least it'll give you experience. Work in a charity shop, then at least you can say you have experience in retail. Is it a relevant job you want? Or just the money? I'd apply to any job you find, anywhere. Chances are you'll get at least one of them. And then at least you have job experience so you'll be able to get your next job.
4) Driving theory test books - and make sure you practise hazard perception. As someone with a good memory, the rest of the test was fine, but hazard perception was a beast...