Both lights - 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.
Clearly the BS (or equivalent) only applies to steady lights.
The only requirement for a blinky to be road legal is that it emits at least 4 candela and is correctly positioned.
I would think that the CE mark constitutes an equivalent EC standard or can be assumed to.
In either case fitting any blinky whatsoever (4 cd+) brings you inline with the legal requirements.
The catch here is that this only applies if the blinky DOES NOT have a steady mode, if it has a steady mode it then has to comply to the steady light requirements.
Anyway, why the paranioa ?
Are they following you again ?
