So the end result was this, a mate who is a shipwright (and whom I embarrassingly never asked before) came down and had a look.
The leak is not major from the drive and he tightened it up to no more than one or two drips here and there. When the boat is slipped we will drop out the shaft and redo it all but there is no rush he assures me.
After building some temporary baffles and letting the boat sit for 24 hours or so (Bilge alarms in every baffle space) we found that the water
was coming from the bow section (forward of chainplates). We sprinkled some talc around and found it is coming from under the water tank.
Unfortunately access is poor without removing tank, so we stopped to think for a while and drink a bit, we never got back to chasing the leak but we removed the baffles so all good with pumps, removed talc etc.
Now I need to dismantle the floor and look more but in the meantime I am confident (and more important my shipwright mate is confident) that we are looking at a small problem that will be hard to find. I just need to make the time to get it to happen. Preferably this week.
Thanks for all he advice and thoughts, very much appreciated.