Thanks for the tip Richard. I didn’t really give the fog light that much attention. Thought I copied how it originally worked when I had to temporarily rewire it but it has passed the mot a couple of times like this.
I think the only MOT requirement is that rear fog light(s) have a warning light when on. Sadly this is insufficient for many

I like the one touch latching system on later cars which means the rear fog selection is lost when ignition is turned off.