OK, firstly I got the CE mark bit wrong. Yes, it does look like any light that is CE marked is therefore legal.
That adds a set of front and rear blinkies branded by the RAC into the mix.
Re the legal smallprint...
The Road Vehicles Lighting Regulations 1989 (
Statutory Instrument 1989 No. 1796)
The Road Vehicles Lighting (Amendment) Regulations 1994 (
Statutory Instrument 1994 No. 2280)
The Road Vehicles Lighting (Amendment) Regulations 2005 (
Statutory Instrument 2005 No. 2559)
The Pedal Bicycles (Safety) Regulations 2003 (
Statutory Instrument 2003 No. 1101)
Unfortunately the British Standards aren't freely available, but BS6102 part 1 (called up by Pedal Bicycles (Safety) Regulations) deals with the bike as a whole. BS6102 part 2 (reflectors) and BS6102 part 3 (lights) are called up by the Road Vehicles Lighting Regulations.
Now I have gone through the 2005 ammendment to the best of my ability (well, until my brain stared to dribble out my nose) and as far as I can see, there is no mention of blink rate, but the minimum limit of 4cd is mentioned. So I presume the blink rate MUST be contained in a british satndard somewhere. The reason I say that is because of this site...
www.audax.uk.net and inparticular
this page which states:
The exact specification for flashing lights is, flashing between 1 and 4 times per second, with a brightness of at least 4 candelas.
What I also found interesting was this:
A forthcoming amendment to the Highway Code will recommend that a bicycle fitted with such lights [read: flashing LED], should also be fitted with a steady headlamp when used on unlit roads - but this is a recommendation and not law, it does not mean you need a steady light to be legal.