Help me write a letter to my GP

As mentioned on here before, my GP surgery has reduced the amount of meds the prescribe me, not on medical grounds, but I believe on cost-saving grounds. The pharmacist in the pharmacy that is joined on to the doctor's surgery recently complained to me about the cost of my meds, and this isn;'t the first time.

The neurologist prescribed me migraine tablets and says I can take one a day as a preventative, but the doctor will only prescribe 8 a month. This is the med the pharmacist complained about - they're £12 a tablet.

Also they recently cut the amount of eczema cream and soap substitute I'm prescribed in half. Again - no medical reason for this. It's just it costs around £20 a bottle so now I'm only allowed one bottle a month instead of two.

I'm writing to the GP to ask him to reconsider, can someone help me? What should I say and how should I phrase it? Would it be going too far to mention that the pharmacist has (publicly, in front of other patients) shamed me for the amount my meds cost the country? Would it be too emotive to say "I know I'm costing the country money but I need these things"?