Simon Autos came up trumps with the manifold spacers and the seals, (plus the small hoses around the carb) but when I took out one of the seals, this is what I found:-
Initally I thought I had nipped the seal when trying to remove the front hose on the manifold, but now that I have it out, I can see that it appears to have been like that for a very long time (21 years in fact ) Although it looks bad, on close inspection it does seem to have been making a reasonable seal,
Anyway, the weather has got a bit warmer so I am starting to put it back together again.