I can recommend Olly Penrice’s place in the south of France. He is is an astro-imaging specialist: https://www.sunstarfrance.com
The best location in the south of the UK I have found is Llanerchindda Farm, run by the Hadley Family in mid-Wales. They don’t have much equipment there (they have a 6″ Dob) and they are not astronomy specialists, but they are very helpful. https://cambrianway.com