You dont have to be in full time education to get free prescriptions.
If you're 19 or over, you're not entitled to free prescriptions in any case, whether you're in education or not.
Ask your pharmacist for an HC1 form, you can fill this out in an attempt to get free prescriptions. However, you have to declare all your money, savings, earnings etc, and by the time you've done this I doubt you will get anything free if you're on a gap and working...I filled out an HC1 form, earning £40 a week from a part time job and paying stupidly expensive rent in Uni residences and I still got sweet FA from them.
I would just grit your teeth and pay it...the HC1 form is worth a try but like I said, they are quite mean. Fraud isnt worth it, if you get found out you will get fined about 20 times more than one prescription cost....not worth it!