Finally got round to re-sealing the camshaft cover; smeared some sealant on the mating surface on the head and then onto the cover (and around the outer edges of cover), put the rubber seal onto the cover and refiited cover, so to sum up , I have effectively got sealant on either side of the rubber seal and around outer mating face of the cover, hopefully this will be ok and stop the leak?
Cheers Pete