Front Lamp
One is required, showing a white light, positioned centrally or offside, up to 1500mm from the ground, aligned towards and visible from the front. If capable of emitting a steady light it must be marked as conforming to BS6102/3 or an equivalent EC standard. If capable of emitting only a flashing light, it must emit at least 4 candela.

Rear Lamp
One is required, to show a red light, positioned centrally or offside, between 350mm and 1500mm from the ground, at or near the rear, aligned towards and visible from behind. If capable of emitting a steady light it must be marked as conforming to BS3648, or BS6102/3, or an equivalent EC standard. If capable of emitting only a flashing light, it must emit at least 4 candela.

I would take it to mean that any light with a 'CE' marking is therefore legal over here ?

I have a cheap halogen Sigma headlight (5 x AA) on my bars it's good quality but light output is poor.

I guess that makes my setup legal - even though there isn't any point in turning it on, it's totally swamped by my other lights.

I'm going to have another go at getting the halfords light to work - all the electrics are in the battery cover and the connection between this and the lamp is pretty poor. Last time I used it it went out and I fell off the road.

I guess I have to choose between lights that work and lights that are legal......

The sigma is an ok cheap buy to be law abiding, I might even leave mine fitted but just not bother to turn it on.