Spent the bank holiday installing the new timing chain/guides/tensioner, service manual print outs in hand and triple checking everything.
All sealed up now, should be able to get the engine back in next weekend, all being well.
Chain that was on was stretched - not by as much as some i've seen but the main difference I noticed is the chain tensioner was quite far extended whereas the new one is much less extended, maybe it couldn't take up the slack or something jumped on first start. Anyway, hopefully this is all sorted now.
Also changed the crank pulley seal as I don't ever want to be going in there again!