Well, I have the same problems as you, OP, if not worse, but I seem to cope. Here's my advice:
Revise, revise, revise. Don't try and juggle a social life AND exams.
So you haven't got a gf? So what? What's the percentage of people in the UK that are single? If all of them felt depressed because they're single, then it'd be a sorry state of affairs. Wait for uni and then find one.
You don't have a job-another so what. I haven't and I get by. It's all about not being materialistic until you have the money to be able to be.
Above all, keep positive. If you feel depressed, read some inspirational quotes, literature, anything to perk you up, even adopt a motto that you can write each time you feel low.