I hope your GP can sort it out, but if you do end up needing to buy them, try 247ukchemist on eBay. I had a broken hip last year and like you couldn't keep going out to buy it although I was on 3 maximum doses a day. Before they sent it, they asked me this:
'Please confirm the person using this product, is familiar with their condition, the correct use of the product, will follow the patient information leaflet and any important advice provided in the listing, is of the correct age to use this product(s), not allergic to any of the ingredients, is not pregnant or breastfeeding and will consult a health professional if their condition does not improve or gets worse.'
I explained my situation and then they were okay about sending them in larger quantities.