One of the first things I'd try, if he was my dog, would be changing his food. I'd try James Wellbeloved: www.wellbeloved.co.uk
Another good one is Burns: www.burns-pet-nutrition.co.uk
My preference would be JWB for him, being 6 months old - I don't like feeding pups on Burns because I've had too many lose weight on it, although ingredient-wise it is excellent. Burns adult food is excellent too. Burns also don't make a Junior food, while JWB does (for pups from 6-12 months). So I stick to JWB for pups until they are 12 mnths and then often switch to Burns, or continue with JWB, depending on the dog.
If she wants to feed a wet food, Nature Diet is excellent: www.naturediet.net