UPDATE:
I've been visiting family and friends up in Lancashire last week, including FOC member J_DUB, who i've known for a few years, was good to see you and the family John.
Anyway, whilst up yon, i got a call from Kev the Dyno man, asking me to pop in to his place when i get home, which i did last Friday afternoon.
The head was still off, because he wanted to show me what he had done to it, plus some pics he had taken from when he stripped it, (i'll get them off him and post them on here when i get the bike back, so that you can all gasp in amazement...or not!).
All of the valves were coked up badly, cylinder no3 was showing exhaust gas blowback into the inlet ports, which means the valves were sticking open, as he said, which explains the lack of compression on that cylinder.
There was also a largish pock mark on the valve seat (i forget which one) but he's ground all of the valves in and cleaned those and the piston crowns, which were also badly carboned up, the cylinder bores were ok.
The head gasket is being replaced (obviously) and new valve stem seals fitted, might as well do those while the head is off, they aren't that expensive.
By the time i ride the bike home, probably later on this week, the final bill will be around the £500 mark, i know it sounds a lot but he is one of the best and the bike will be 100%.
As i mentioned, i'll post the piccies and the Dyno sheet when i get them.
G ; )