Update, I have put a new barrel, pistons (JCC), rings (Goetze) and the head has been done and it is all back together. I have given it a run of fifteen minutes ( no warm up just off and up the road, no idling, no lugging , up and down through the box not exceeding 4K and up and down hills ). No smoke, no odd noises and started first kick, let it cool overnight and retorqued the head and did the valves again and gave it another squirt and all good so now just need to monitor oil consumption and keep fingers crossed. Still don’t know why the exhaust valves were tight. I checked the sump and there was 150 mls so it is ok too, thanks for all the assistance given during this saga it is greatly appreciated. Cheers.