Thanks Tim, informative as ever. I feel much happier now. I don't suppose you know where I can lay my hands on the rubber oring to plug the small gap at the top? Would something like silicon sealant do the trick?
I might have a couple of the foam fillers but they are a sod to fit once the fork is assembled. It might be better to fit a large dia small section standard O-ring, I will check if I have one suitable