I have an eight year old dog who has only ever been a family pet, he has a very good pedigree and is very healthy. I wondered whether he would be of any use as a stud dog?

Don't wish to dampen your enthusiasm, but probably not at his age - sperm count is inclined to tail off (unitentional pun :_) ) as the dog ages. If he is a really good specimen of the breed, go back to your breeder and ask their advice .
Be warned, usually a dog gets known, and breeders will usually approach them; a stud dog shouldn't need to advertise, though I dare say a few good dogs have been ignored as their owners were a little retiscent!

Jo and the Casblaidd Flatcoats