My 2002 Plus8 had similar rear fog issues. Traced to the PCB/eprom unit behind the dash.
I opened the casing up, pushed the eprom down to make sure it was in properly. The board was rattling round in the casing as the glue failed. I restuck it and the fault went away.
In the meantime I was trying to source a possible replacement...factory had a stock of units for pre 1998 cars but none for post 1997, they were " on order".
After ordering via Melvyn in January I cancelled in September as I had fixed mine and none had come in via Morgan to Melvyn! My MOT was due so I came close to rigging a bypass circuit. I spoke to Mike Baldwin at one point re using the ones they had in stock but he said they wouldn't suit. My alternative was to buy one from a supplier like carbuildersolutions or similar as they sell a lot to kit builders. Only issue then would be matching up the wiring...and we all know the Morgan issues with that!
Good luck sorting yours out! You may get lucky like me.
