Thanks everyone for the advice and concern
We went to the vet who took some skin samples and combed through all his fur ... There are no mites, fleas or flea eggs, but his skin samples showed a bacterial infection, so I have been given some Neotopic - H (hydrocortisone) cream to use for 3 - 5 days and if that doesn't help (which it does seem to be working) they will give him some antibiotics ...
Now all I have to do is find out what's causing it