Thanks Martyn, Dave and Roger, and others who have made good suggestions. I will try these techniques and feed back to you what works.
I have decided to do a paint job on the deck (given up on trying to match the colour and having used epoxy resin, I ned to protect it from uv), so the next step is a bold one, remove all the bolts and take the stem fitting off! Expect to hear muffled swearing from under the fore deck while I (or a passing slender female who enjoys beer) try to fit it back in a few weeks time.
Spike