Hi Martin
I received your PM.
My advice would be to crack on with the GCSEs as soon as possible. The beauty of the night classes are that your days will be free to work, hence earn some cash to convert to flying/beer!
As mentioned, age is most certainly on your side, being only a couple of months under 17.
Let's say you get the job at Morrisons or anywhere else for that matter. With minimum wage you should be able to crack £500 per month. Take a little off for food/bills/rent to mum and you should still be able to square away about £300 per month.
PPL = Approx 40 hours flying.
£300 = approx 3 hours instructional time in a Cessna/Piper working towards your PPL. (Even cheaper flying through one of the clubs BEagle pointed out!)
If you do 1 trip per weekend and dedicate the other weekend in the month studying towards the PPL written exams you could feasibly complete your PPL in just over a year.
You will then just be turning 18! You will have your PPL and your GCSEs will be well underway.
This is a great situation to be in. You will have found out if the RAF is taking on FOAs. If so you've got the option to then join and use your RAF wage to continue building your flying hours (the RAF will also pay for studies such as GCSEs and A-Levels). Or, you can decide if you'd prefer to pay your way through flying training whilst keeping up the studies too.
There are lot's of pros and cons for every choice so don't be afraid to ask for advice on this forum. There will almost certainly be someone who can help.
Best of luck with the job application!
TF