The conversion uses dual filament lamps kev, the dimmer one being for the tail lights and the brighter filament for the brake lights. They still work as fog lights when required.
To be honest, I don't really care that it contravenes the road vehicles lighting regulations, I reckon that making you more visible when braking has to be a good thing. It cant be that bad as this is standard on JDM spec cars. It doesn't dazzle anyone because the larger filament used in the twin filament lamps is exactly the same wattage as a regular fog light lamp. I will probably get some replies saying that the reflector design is different on fog lights making them brighter blah blah blah, but if you follow a car with this done, they are no brighter than the brake lights.
It is not really going to cause anyone a problem until MOT time anyway, unless you get a very clued up police officer :D :D :D :D :D
For your MOT it can be reversed by simply disconnecting one wire.
Yet another stupid British law...............