So a bit more time spent on Sunday.
There's an exhaust stud which was broken at what was probably the manifold flange. It wouldn't budge before so I managed to run a thread die on it and cut enough to get a flange bolt on and then a nyloc. I tightened them together and eventually got the broken stud out which is a result
I dropped the cams in ready to check the valve tollerances - found out I lost one of the cam journal bolts and the cams don't look to special, still they're in for now and I turned the engine over 720 degrees with nothing locking up, so result no2.
So that puts me back to where I was before ... and on a little because the chain guide fouled up last time

After a few sleepless nights I think I'll look for another head / cams. I'll look to get it flowed properly rather than my bodging attempt, don't get me wrong I enjoyed it but I'm quite aware that I don't know what I'm really doing. I'll start the motor and run it before swapping things around.
As if by magic a side car engine turned up on the bay and some Yamaha gaskets - it's been converted to right hand gear change so that's something to have a look at.