I'm probably repeating a lot of whats been said already - but to reiterate:
1) ATPL theory is not complicated and probably around GCSE level. Its challenging, but due to the volume of information, not the complexity. If you were accepted onto a degree course in Aero.Eng I have no doubt about your ability to pass it all with no issues.
2) You don't need a degree to be a pilot in the UK. Many of my colleagues don't, and they are 3+ years ahead of me in their careers and not paying off very expensive student loans.
Go do some private flying. I'm sure this will boost your confidence and tell you whether you really do love it or not. From then on, your next move should be fairly easy.