NO, you don't need A levels.
I have a handful of GCSE's and a load of experience in a totally different field. I went on a CAP509 and got dead lucky.
I guess that luck and flying school results, combined with a bit of BS will help.
But, try your best and if you make a bollox of the A levels then don't highlight the fact to future employers. Play on your positives.ot your negatives.
Good luck.