As I understand it with an EASA licence, the country of issue and the medical records have to be from the same country.
So if you left it all with Portugal you would have to find an AME who could issue a Portuguese Class 1 medical in the UK, or go back to Portugal every time to get a new one (no prob if you travel there regularly)
But if you changed the licence to UK issue you could do it with any old AME who could issue a class 1 in the UK.
Correct me if I am wrong........