Thanks folks - yep I have RTFM and as far as I can see it says FA about the oil seal.
I was wondering if it's an engine in, easy job or an engine out job hence the reason I was after an exploded view. I've got the crankshaft pulley off and there seems to be an oil seal land on the shoulder of the pulley boss - but there was no sign of a seal in place, knackered or otherwise. The only seal I can see is deep inside. Is this replaceable with the engine in situ?