There are other places that no doubt get it but not sure where. It’s a very sticky clay type that just sticks to your bike like nobodys business
just like this, check that rear tyre.

(thanks grahamh for the pic)
So what options do I have? as thin as I can go and hope for the best? find new trails? MTFU and remove the mud every 50m? Maybe develop a tool to efficiently remove the mud from the tyres.
Currently have 2.1 Mud-X but they do effectively nowt in this stuff.

Maxxis Wet Scream? Could well be your only hope.

Skinnier tyres and singlespeed?

(my choice would be to ride on the road until it dries out though!)

Avoid the trails that get like that. You can’t be doing the trails, or your bike any favours getting in that state.

As a fellow cotswolder my tactic is winter loops that avoid trouble spots, stay high in the valleys and hit the mud only when its frozen solid. Mudx are fine for this rule of thumb. If you like the mud panaracer trailraket is your friend.

Consider spraying the bike and tyres with WD40/GT85 before you start out.

They used to use Pam cooking spray on the bike in the USA for muddy races.

The only way to deal with Cotswold mud is not to go anywhere near it.

You can try any tyre, any frame, any gear configuration and they will all fail.

Sorry but 20years of dealing with the stuff has led me to that conclusion.