Hi Helz
not sure that is legal, MOT or Plod could be wrong but They should only be able to work when sidelights are activated, and independantly of each other no sides no foglamps, my last car failed mot cause fogs worked on their own, the tec said they need to be activated by the lighing circuit.
Plus how many times do you use your rear fog, me I think once in eight months but could have done with front fogs quite a few times in driving rain, I also think you should know that driving in clear/murky weather with yor rear fog on is an offence it has to be foggy/heavy rain with reduced visability, wouldn't want you to get into trouble with the boys in blue, don't know what they are like down your end, but here in Wales they will do any one to make a buck, plus you may burn out the rear fog switch cause it is carrying to much power, wasn't designed to operate front and rear lamps,
I am going to track down another fog lamp switch same as dash mounted one complete with plug in back and turn it upside down mount it next to the rear fog switch and run it throught an aftermarket relay to the lamps with a made up loom, once I have finished the elecy mirror project