Thank you all for your comments - my first action will be to have a chat with the engine reconditioner - who is a reasonable sort of guy ( even though he is a Kiwi!!!) I just wanted to understand what was a possibility. The link was great Joe, esp the info re the e hidden bolt. On second thought, I think I shall clean all the oil off and try and nail exactly where the oil is coming from then off to the reconditioner.
Cheers