Thanks guys,
Its registered on an 1982 plate (date when it was ambi converted not built), so strictly I do need them unless i go through the hassle of getting my v5 updated first..
I looked at the wiring, and realised that the rear fogs arnt actually in the loom proper, as they were an ambulance addition... Cable is cable tied onto the chassis, and doesnt work because i've cut it when i rewired the truck as i didnt know what it did! (i rewired everything except the front to back stretch which i just plugged into). I had got confused while wiring and had run a fog light feed through the wire to the convoy light (which evidently has a dead bulb!)
I then remembered that i had bodged the fog lights back when i last mot'd it before rewiring it - and have dug out the old bodge and rebodged it again using a wire running inside the vehicle.
Hopefully it will pass!
Having had to change a bulb today and unscrew a light, there is very little left of the back sections of my lights if you pull out the rubber inner section, so i think i could quite easily paint them and pretend that there wasnt supposed to be a light there!