Is your son a type 1? If so he should be checking about 5x a day, more if he is ill or has anything like unexpected exercise, meal out etc. It is terrible that doctors are doing things like this, if they want to save the NHS money then they should look at their massive wage packets, especially GPs, not do it at the expense of patients' health.
When I did DAFNE my nurse gave us each a letter explaining we needed to test 5x a day, and also if we wanted ketone strips or to change strips or insulin or whatever because of what we learned on the course. Ask your hospital doctor or nurse to write your GP a letter saying why your son needs to test and how many times a day they reccommend testing.
Incidentally, I am interested that your pharmacy usually deals with your son's prescription. I would love that arrangement, my chemist is a lovely man and is open til 7pm so I would not have to rush back from work to get there before it closed, as I have to at the surgery. I asked if he could deal with my prescription, I filled out an official form allowing him access to my hospital record, but the GP would not allow it for diabetics apparently.
This may seem like I have an unreasonable bias against GPs, but I feel it is entirely reasonable given the things they have done in the past. Once I went to them wanting to go on antidepressants and the doctor did not let me get a word in, she immediately launched into a tirade about how I would get all these complications if I did not test my blood sugar, she was really aggressive and by the end I was in floods of tears. She did not seem to care, just said I had exceeded the appointment time and should leave. It was left to a fellow patient to console me in the waiting room. Or, another time, I wanted to add ketone strips to my prescription and the GP said they were already on there. Turns out he did not know the difference between ketone strips and blood strips. Or, once the GP wanted me on statins (at 25!). He started looking for some info on why I should be on them. He spent the whole 15 minute appointment time searching online and in his books and found nothing. I could go on. I am sure there are great GPs out there somewhere who work really hard and justify their giant pay packets, and their patients adore them. But I haven't met any.