Paracetamol on prescription

One of my Sils works as a doctors receptionist and always complains about people getting OTC drugs on prescription. Her argument is that paracetamol can cost as little as 19p a packet so people should simply buy it. That's fine if you use it occasionally for a headache, but if the GP has prescribed it for regular pain relief then surely it's acceptable to obtain these drugs on prescription. There are quite a few medications available otc-particularly digestive aids-should we buy these (if we can afford to) in order to save NHS money? Or is it a question of frequency/dosage/amount that is the decider?