All lamps on the car fall into specific categories. Spot lights / driving lights / pencil lights or whatever else you might call them are actually optional extra main beam lights, because they aren't side lights and don't have a fog or dipped beam. All main beam and optional main beam headlamps must be wired like this:
10. Electrical connections–
(a) Every main-beam headlamp shall be so constructed that the light emitted therefrom–
(i)can be deflected at the will of the driver to become a dipped beam, or
(ii)can be extinguished by the operation of a device which at the same time either–
(A)causes the lamp to emit a dipped beam, or
(B)causes another lamp to emit a dipped beam.
(b) Where a matched pair of main-beam headlamps is fitted they shall be capable of being switched on and off simultaneously and not otherwise.
You can have a switch to isolate a pair of optional lamps so that they don't come on with the others, but the dip switch must still switch them all off at the same time.