Trevor, the oil's a milky yellowish consistency with no frothing. I made some on the bench by stirring together oil & water.
I didn't know there were cork rings available for behind the clutch, or did you make your own? Do you reckon cork would be a better sealant?

No idea
Have seen them as felt & neoprene cork
Think I have a cork one in at the moment
Was just a thought as clean dry felt can hold a lot of water

Thanks Trevor. I'll try to find something cork or similar. The felt ring in there now did have water in it. For now it's all going back together.

Well that will be the source of the water which is getting into the oil.
It does not take much to make the oil milky
Get a nice big bottle of the cheapest oil you can find then go for a nice long ride & change the 90ml of oil when you get home .
Repeat as often as necessary till the oil comes out clean, horrid thing to have to do on a nice sunny weekend .
Better still would be a new felt oiled with light machine oil before installed to prevent it adsorbing water
Apparently fabric treatments like ScotchGuard or even a water repellant like WD40 does a good job of keeping the water out of the felt.

Thanks for these ideas Trevor. It isn't all together yet, I can get some WD40 up there behind the clutch. Might even take the clutch off (again)to get a better shot. Wifey currently ransacking the laundry cupboard for Scotchguardy stuff.
It's meant to rain for a while here (about bloody time even if it does cut down the riding) so I've got the opportunity to do it all.