Thanks Brain. That Company in Newark is the one that re-did my RG500 fork legs 10 years ago (and which are still perfect) so will certainly get my repeat custom if needed. As you say, its near impossible to find the right unit and also has a very grumpy owner but they do a great job. The leak isn’t at the valve but seems to be at the top of the left hand fork tube as you can clearly hear it hissing out when pumping the forks. Thanks for the tip about the bushes. I was planning on going to Newark soon as I need some bits and pieces for the latest project donated by my father (British Anzani lawnrider mower).
I like the idea of having a bike thats over 60 years oid that has air suspension. Thus, I will do my best to get it working as Dowty intended. A spring conversation will only be a last resort.
Look forward to meeting up on Sunday!