Paul D is right, you don't have to take the head off to change the tappets - my mistake, been working all hours recently building a race Ford X-Flow which seems to have addled my brain....
I agree with Simon - my b202 engine sounds like a bag of spanners for about a minute after a cold start then, because a baffle has gone in one of the exhaust boxes, it rattles nicely afterwards as well..... had the head off, done the valves/replaced tappets, timiming chain and all tensioners/guides - before anyone starts : )