What is the best dog food I can get for my dog?

I live in England but want to know what is the best i can get him. he has never been a fussy eater but in the last few weeks he went off wet food,just wouldn't touch it,I got him one variety of dry food which he ate but when i bought it again he wouldn't touch it so tried him with wet again but he just wouldn't touch it,bought another variety of dry which he eats eventually but not with his usual gusto. He is not ill ,happy ,lively his normal self except for eating . He did enjoy turkey over christmas mixed with veg but i am not giving him a roast dinner everyday:-) AAny suggestions on a good brand to try ?