This is a well-known topic. I know someone who delivered meds, and he said that lots of patients routinely DO NOT take their meds, but keep on getting them and hoard them (I know, ridiculous, but that's a subset of folk for you . . .they go to the doctor for advice, but decide they know best anyway).
The relatives of deceased patients would routinesly bring back bagfuls of unused meds to the chemist, and the regs say that all must be destroyed.
This is due - apparently - to someone in the Civil Service, or NHS admin hierarchy, having concluded that some demented soul might sabotage their packs of Tramadol, Omeprazole, or Candesartan (etc) with something poisonous so that a tragedy would result if they were re-issued??
IF you have a Labour MP, why not contact them to try and get this massive UK-wide waste prevented?