There are limited uses for the A&P in UK, Polar in Prestwick are always looking for B747 people so You could try there. As for converting an A&P to an EASA part 66 license there is no conversion neither do you get any exemptions if you wish to get this license the present regulations say you must pass all exams and have a further 5 years experience to actually use license priviledges (with the appropriate type rating) though this can be reduced depending on your previous experience.