*waves* I know we've spoken before, but I don't know if you knew that I've just become qualified as a barrister here in the UK? Well, yep! I get my call in July and . . . so I have a lot to say and feel free to PM me if you want to ask more, or if you want to ask any more questions.
OK, so first things first:
The name on your degree will matter less if you want to be a solicitor and you don't want to go to the Magic Circle (the top commercial firms in the UK -- Slaughers, Freshfields, Linklaters, Allen and Overy, and Clifford Chance). Outside the top commercial firms, it matters more that you get good grades and good recommendations from your professors, and that you've done things other than study for your degree (volunteering, societies, etc.)
It's (mostly) true that if you want to go to the Bar, you'll need an Oxbridge degree (and probably a master's from an Ivy League uni). Next best degrees are from the LSE, King's and UCL. I've decided to become a commercial barrister, though, so I'm probably very biassed on the whole thing.
If you want to work in criminal or mental health law, however, the Bar is much more open to you -- they'd rather see good grades and community involvement from a decent uni than see just the name on your degree. Also, if you want to work in mental health law after you train, then don't discount your experiences with mental illness as a means of getting to uni even if your A-level grades weren't so good -- and especially if they were a long time ago.
And don't worry about the money hungry lawyer image! It's only like that if you go into commercial law; rest assured that you'll live a life of near-penury if you decided to do the kind of work -- criminal, family and mental health -- that is financed mostly through legal aid.

Law is a good degree to have even if you don't want to be a lawyer! Conversely, you can study ANY degree at uni, and then convert your degree to law afterwards on the Graduate Diploma in Law (GDL). Sometimes it's possible to get hired by a firm of solicitors or selected for pupillage by a barrister's chambers and they will pay for the GDL and your LPC (Legal practice course -- for solicitors) or BPC (Bar Professional Course).
The law is kind of an obscure profession

I can explain more the routes into becoming a solicitor or a barrister, if you're interested. Just remember that people with law degrees do almost any job you can imagine; I have former classmates who did everything from becoming magicians (seriously) to investment banking to journalism to organising the occupy protests.
Definitely do voluntary work; it'll be good on your CV no matter what degree and career you want and it looks fabulous on your UCAS statements. It may be possible (depending on where you are in the country -- most lawyers are in London) to observe barristers or solicitors at work for a day or two; you can check on their websites for more information. Also, MIND run legal advice and advocacy services that are always looking for volunteers and that would look fabulous on the CV of an aspiring lawyer.