For your initial license issue you have to have a medical from the state of license issue. I am not totally sure but I do think that you can do say your initial medical in Spain for instance and then revalidate/renew it in the UK and have your license issued by the UK Caa. Obviously it will have to be revalidated/renewed to the correct country before license issue could take place. In fact I am 100% sure that this is correct as I know of a person who has done it. Lots of people do this sort of thing to get around eye exams etc where the limitations in all the Jaa countries are not the same with some being less stringent than others.