Quite a number of commonly prescribed drugs (eg blood pressure, Levothyroxine, etc) are available over the counter at French pharmacies fairly cheaply as long as you can show the pharmacist the UK doctor prescribes them for you so either keep a packet with the pharmacy label on it or be able to show them your 'repeat prescriptions' list so either your entry on the NHS App on your phone, or the physical other half of the last UK scrip you had filled for them. Most pharmacies employ people who speak other common European languages, we've always found. If you do need a prescription abroad, it always costs money to see a and get the script - usually around 25 to 30 Euros in France, just the same as the locals pay. Plus then the cost of the drugs at the pharmacy.