You say it WWW!
I left school at GCSE level with 11 C grades. Not bad. I did A level for a year but I found it so boring, I left. I don't regret it at all. Pilots don't need any formal qualifications, except their licenses and ratings. Fly boy, don't go back to school, you are on the right track, you have a job, (that you appear to hate) but so do I. I have several jobs, at the weekends I deliver Chinese food and make £300 a weekend, that pays for my petrol and 2 flying lessons every weekend)
Also, I imagine you have a bank account. If so, make sure you save everything you can into it. If you ever need to apply for a loan, (HSBC) it will be helpful to see that you can save and manage money.
Like me you are 18, we both, like others have chosen one of the hardest careers to get into, but the rewards are endless. Don't go back to school. There are good pilots without GCSE's. Plenty of them. (Ask Oxford!)
Anyway. Good luck fly boy.
P.Savage