Thank you everyone for all your comments and suggestions. I will take them all on board. Re the last vaccinations: the vet held off on doing these for a few months while he was on the Macrolone. When he decided we wouldn't wait any longer, I took Nicky off the medication for a few days before and after the injections. Back on again now.
I can see this is going to be a long-term proposition. The strange thing is I had a Rottweiler about 10 years ago who suddenly popped out in scabs on the nose, ears etc - took him to the vet (same vet) can't remember the treatment but I think it consisted of an injection and tablets and putting Betadine on the scabs and the condition cleared up in a matter of days never to return. Unfortunately, this was before the days of computer records so we can't check on the treatment. In that case I am sure it was caused by stick-fast fleas. With Nicky there is no apparent cause. There are no fleas on this block so he does not get any flea treatments and rarely sees any other dogs.
Thank you all again for your advice and replies.