Alrighty
I put the engine up on the stand and was checking out the timing cover gasket. It wasn't quite the right shape when I put it on and I thought it was possibly leaking water where the water pump feeds into the block. It was in perfect condition when I pulled it apart and had no signs of leaks so I bolted it back up.

Next cause of concern on the list was the head gasket. I cleaned up the bottom of the head again and the top of the block. Dug out my old drawing set square and both surfaces were perfectly flush. I cleaned up the head gasket and bolted it all back together. I wanted to see what would happen when the water pump was running so I knocked up this adapter. (I can't bolt up the flywheel/starter while it's on the stand)

So filled it up with water and turned it over with some Bosch power. Water started spewing out of the camshaft bearings and down the rocker arms. I'm guessing it came up the head bolt holes

Video link
http://www.flickr.com/photos/55685928@N03/6271194058/We weren't sure if the head gasket wasn't sealing or if it was something else. To eliminate the head gasket it got sealed up with liquid gasket goop and bolted up together again. I didn't put the camshaft or rockers on the second time to pinpoint the leaks. I was pretty sure it was the gasket now, as it all worked fine before. So this morning after the goop cured I gave it another spin with the drill, and it was all good, no leaks anywhere.

For the last few months I've had the gold wheels on one side and the black on the other. The black side has been facing out for a change and I'd forgotten how much I like them...

I'm thinking the cause of the leak was the brake cleaner I used to clean the block and head before we bolted them together. It's a bit more harsh than the usual degreaser but dries quicker and cleans much better, which is why I used it. When I cleaned the gasket before using it the second time it dissolved the clear layer, which I asume normally helps it to seal.
So I'm going to order some new gaskets this weeks - head, exhaust, sump.