First, check your PIP award letter. Look for the daily living bit. If it’s there, download form HC1 from the NHS website. Fill it in, mail it, and wait for a shiny certificate.
If you don’t have daily living, apply for the Low Income Scheme anyway. You might be surprised. And if you’re stuck, ask at your GP surgery or a local Citizens Advice. They love this stuff.
Also, do it soon. Prescriptions cost like £9.65 each now. That’s robbery for a box of paracetamol. Don’t let the system win.