Theres not really a right or wrong answer, you've just got to make your decision and see how things turn out. Things did'nt go too well for me so I am now going back to Uni to get a degree.
When I was 21 I started a degree in Physics but when the funding became available I quit that to go and do my long dreamed about flight training (fATPL) at Oxford. Unfortunately myself and a couple of others, in a declining pilot market, never got a nice airline job so we were left with seeking an FI job (if you could afford to get certified) or like me had to go and get any job I could find because I'd spent all the family silver on flight training and the banks wanted paying back and the bills needed to be paid.
Now with just A-levels you cant get a very well paid job infact the highest paid job I could find was in a warehouse, at this point I'd wished I'd finished my degree at least I would have been on £20k to pay for continued flying. I saved my money in the hope of becoming a flight instructor in the US but 9/11 put an end to that (also you cant get a student visa in the US if you already hold a CPL
)
So with the pilot market looking bleak for the next few years I have taken the advice of one airline recruitment chap who I met at an airline interview (it was Aer Lingus or Britannia I cant remember which) I asked what I should do now you've just turned me down and the job market in decline (and this was pre 9/11), he said "think about getting a degree". I asked what kind of subject, he said "any subject, just get a degree it'll stand you in good stead later on" and thats a true story. I met a guy in the US who went from the right seat of an A320 one week to a B&Q type hardware store the next due to 9/11, he had no back up qualifications but still had a wife, 3 kids and a huge mortgage to maintain, scary.
I'm now 26 and going back to uni to do a 3-4 year Aerospace Engineering degree, I've no idea whether it will help me with my flying career but I know it will help me if I'm ever on the totally pennyless pilot job que again. Its like that other chap said above, no-one can take a degree off you but you can lose your licence and if the pilot market ever bombs again, maybe even in 20 years time, you'll have that back up and believe me 3-4 years literally does fly by. And if flying doesnt work out you've got a possible back up career which can give you an equally easy life (my brother got a degree in chemistry and now he's a bio-chemist working for NASA on $80,000 a year living in California
) its not flying but he doesnt hate it.
I just thought I would give you a look at how things can go wrong and how it is always good to have options even if you never have to use them. If a bank will offer you money now they'll certainly offer you money if you've got a degree and are a bit older and hopefully the job market will be recovering. At the end of the day follow your heart, if things work out, great, if they dont then like me its never too late to go back and take things as you need them.
As a last point, once you hit 25 your considered a mature student and you get all your tution fees paid for.