well, after a 1 month saga (of which i only spent about 15 to 20 hours working on the car) of success interspersed with issues, my engine is finally back in and running after my starter fell off and left a snapped bolt in the block! Have been driving a little bit gingerly since Saturday, keeping an eye on the fluid levels and listening for any suspect rattles (other than the usual ones!) etc, and other than having to top the collant up a couple of times, which isn't exactly unexpected, it's all looking good... so...

Thanks to:

Ken for the replacement bolt (and nuts!)
Everyone for the advice on cam cover sealant, clutch forks, getting the remains of the bolt out in the first place
My dad for general advice, trying to keep my calm when i was losing the plot with it, and providing a third hand every now and again,
My mate dangerous dave with his air chisel for finally removing one of the bellhousing nuts,
Everyone who pointed me in the direction of the excellent engine removal/refitting guide, although I would say in addition to the clutch fork bit being missing, I didn't remove the headers, just disconnected at the downpipe.
All the people advising me about how to remove/refit the front drive shafts so i could actually get at said bellhousing nuts - especially the guy who pointed out that they only go on one way - didn't stop me putting the shafts back on rotated 180 degrees from where they should be, but at least it helped me figure out what i'd done relatively quickly.

Think that about covers it - impossible to name everybody, but apologies if i missed anyone!

Next.. rear coilovers.