Replumbed coolant pipes to the LPG vapouriser so that it will switch over quicker and whilst there gave the coolant system and heater matrix a good old flush out!
Also replaced nearside cam cover gaskets with new (genuine) ones as No 6 was swimming!
but as I only had one set of new gaskets and 2 sets of old gaskets I fitted the best of the old ones to the offside as there was a small amount of oil there as well and a slight leak on to the coolant pipe.
Guess I'll have to revisit that at some point.
Also noticed that the oil cooler plate was weeping but left for another day as didn't have the sealant. Might change the oil cooler as at 220,000 miles and as far as I know the original, it's probably due to pop soonish!
So more what I've done over the weekend, but all back together now and running. I've only tested it a couple of times from dead cold, but so far the LPG is switching over quicker than it's ever done!
Thanks to JamesV6CDX and Kevin Wood for the tips and advice for the vapouriser replumb!