Great stuff, looks like its heads off   lucky I know my way around these things (well i THOUGHT i did...)  thanks for the pic Owen, what book is this from?
 

OK so I know I have a clear run to the base of the cam.  The oil then goes up through the cam to the rockers.  Here then is the problem  I'll check the cam bearings for alignment, then check the cam itself as it was reground, could be blocked upper journals, hopefully my custom Clive cam (a damn nice piece of work) is all OK

Ok plot thickens but some good news.  I spent the morning putting the bottom end back together, after lunch I started on the top end.  There is oil at the cam, and it is being fed to the left side head, not the right hand (passengers) side head.  According to Owens diagram, there is a top end oil feed from cam bearings 2 and 3.  Pushrods out they are all clear now blue hazy and rusty at the top so they will be swapped.  Rockers surface rusty currently looking for the cause and the search goes on...... 

Right head now off.  Lifters removed all faces still nice.  All lifter holes clear.  I ran a flexi wire through the holes in the lifter tunnel, all clear.  I took out the grub screw above number 2 cam bearing and ran the wire down, it was clear.  The plug at the dizzy end of the lifter tunnel is still fitted.  It seems the oil isn't getting to the windows in the lifters on the right hand head.  Starting to go round the twist here 

You should be doing all this while turning the oil pump with an electric drill, it will give you 100% proof that oil is getting where it should. Also, is there a reason the left head is off first(or at all)when the right hand is the one without oil, or is the right hand one off already??

Cheers

Ok fixed the left/right thing (it was the right side head I removed......) I have been cranking on the starter so I'll give the drill a go

Lack of pressure can be caused by a blockage, but also by a hole thats not meant to be there. The fact that there is oil to one side means there is a problem on the dry side above the cam. Look for a blockage and/or a hole. (or a crack).

OK ran the drill on the pump shaft for about a minute.  didn't see any oil movement at all. 

Did you try both directions?

Mmmm no, my drill is not so advanced.....