Unless you are wishing to apply for sponsorships which require them or the forces, in my opinion, they are of little use when it comes down to job hunting.
That said, in the current climate, they might give you something to do whilst this recession blows over. They do offer you something to fall back on and allow you to progress your career into other areas if all fails on the flying front. You should take a look at your position and weigh things up. If you're at the age where you're making the decision to either stay on at school after your GCSE's - I'd suggest you carry on with the A Levels. Many say that you can never have enough qualifications.
Some people say that if it comes down to an airline having two similar candidates, one with a levels, one without - they'll choose the one with. That probably never happens, and even if it did - they'd choose personality over high school education. Person a might have 2 A grades in Maths and Physics but he's a right pillock - his qualifications wont get him the job.