Did you ask the GP practice not the GP himself but the practice business how much they would charge to write the letter for you? Not in the terms of offering a bribe but in terms of the making money for the business? I am sure they would throw a price at you or perhaps agree to do it for a donation to the charity box. if you made that suggestion. I put a £20 in the collection box for I think Cancer Research it was at my GP for printing my vaccine passport nhs thing on paper for me as I could not use the I Phone too well. It took the staff member a good 30 minutes tinkering about and running back and forth to the office for me I was more than happy to be generous to the charity box as they would not take money directly.