i do believe that they are illegal as spot's have to be arranged in pairs
No. The letter of the law for auxiliry main beam headlamps is that they must be fitted symetrically. A single lamp in the centre of the car is symetrical. There is no upper limit to the number of auxiliary lamps:
REQUIREMENTS RELATING TO OPTIONAL MAIN-BEAM HEADLAMPS
Any number may be fitted and the only requirements prescribed by these Regulations in respect of any which are fitted are those specified in paragraphs 7, 10 and 12(a) of Part I and, in the case of a motor vehicle first used on or after 1st April 1991, paragraph 5 of Part I.
Driving or spot lamps are optional main beams, not dipped beams so there are very few regulations on installing them because there are regulations about when they may be used. They may be higher than the dipped headlamps, how many trucks do you see with them on the roof? Trucks go through a lot more stringent and regular testing than cars.
There are more regulations for fog lamps regarding position and alignment and there is a maximum of two for cars built after 1991. These are restricted to a max height of four feet, which means you can still have them at roof level on a Mini and can indeed be higher than the headlamps. They must be within 400mm of the vehicle side ONLY if they are being used as replacement dipped beam lamps. If they are wired so that they can only be on with the dipped beam and not independantly there is no lateral position requirement. Of course fog lamps only really work if they are used without dipped beam lamps so that would kind of defeat the purpose.
The most important lamps on the car are the dipped beam headlamps and there are many regs covering them. All other lamps are pretty loosely controlled if you take the time to read the regs.
A search would have revealed all this, it's been gone over many times.
The regs are here:
The Road Vehicles Lighting Regulations 1989
Auxiliary lamps are one of the areas of car maintenance where there are lots of myths and legends told to us all by the same mates who tell us that our spare wheel is part of the MOT. Ignore them all, read the rules.
