You don't need a degree, or even A-levels.
You don't need to do an expensive integrated course.
The clearcut equivalent to 5xGCSEs is to go to evening classes and pass five GCSEs. They're a good thing to have on numerous levels. GNVQs and the like are only theoretically equivalent - in practice they're not.
My suggestion - find a friendly flying school, do your PPL there. At the same time, do the five GCSEs at night school - they're well worth having wherever you go with your career.
Then re-assess: with the PPL and GCSE standard maths and science you're in a position to decide properly whether you want to move forwards and do the ATPL writtens and CPL flying.
Or you may just decide that driving a train is low stress and well paid, and fly for a hobby (or, say, instruct at weekends). You wouldn't be the first, and there's absolutely nothing wrong with that.
G