Jeff,
I didn't particularly "excel" at school. And although I did have to chance to do A-levels I passed over that in favour of a job - a quite well payed one for a school leaver!! And it was that job that got me into flying.
I worked seven days a week to pay for my PPL and looking back its hard to see how it would have worked differently. The prospect of going to Uni and running up a debt held no appeal! Much rather run yp a debt flying!
Jeff, if you want to study for any qualification - GCSE, A-Levels or degrees - thats a good thing. I considered doing something along the lines of an Open University course but its finding the time. Making it more difficult was the fact that I was already planning my advanced aviation training and I didn't want conflicting interests.
I don't want to offer the wrong advise here but if you're on the road to a career in aviation then focus 100% on that. You may indeed excel in your training and find the whole range of subjects fascinating! With regards to jobs I really don't know - but I would say that you will get a job on the merits of your experience and your abilities as demonstrated during selection.
I think its only a problem if you let it be a problem!! Provided you are confident that you can tackle the subjects then you you'll be OK.
You might want to visit one of these Aviation Training Seminars that are held from time to time. I've never been to one but you could try asking some of the companies what they think.
Besides, there are so many different jobs [piloting] in aviation and you are sure to get in somewhere.
Whatever you decide - all the best!!
df1