Thanks everyone, for the the replies and suggestions.
What ever I choose to do it will be slowly. I'll start by trying to obtain a high quality copy on film. This is not something I've done before, so you'll have to forgive me if I'm back asking more questions! I'm very sorry to say his negatives were lost or destroyed a long time ago.
Thanks Whiteymorange for the link, some useful information there. I agree that washing the prints would be a great starting point, unfortunately I can't see how to remove them from the mount without risking further damage.
I've found a Kodak book on the subject which will hopefully get me started.
If I find any useful tips I'll report back!