Axool and Martin, I bought a storm cover from Williams for my 2025 Plus Four.

https://williamspartsshop.co.uk/morgan-storm-cover-203-p.asp

On the delivery note it stated “MMM6180 Morgan Storm Cover NOT CX see notes”…. but there were not any notes. I contacted Williams and they said "Yes the storm cover will fit, they are quite small for the plus sixes but ok for the plus fours."

It certainly fits my new Plus Four very well, and is very easy to install. While it is supplied with a bag, this makes it rather bulky when packed, and I have found it more convenient to fold the storm cover down fairly wide and flat (in a more suitably shaped bag) and slide it behind the seat.

Regards

Guy