Scirocco Central

Hey Everyone.

I'm just wondering if anyone knows about the legality of the programmable LED signs you can get for cars. An example is here:

http://cgi.ebay.co.uk/12V-Digital-LED-C ... 3efc974ef3" onclick="window.open(this.href);return false;

There seems to be conflicting information on t'interweb. These are the two best other threads I found:
http://www.talkaudio.co.uk/vbb/showthread.php?t=167636" onclick="window.open(this.href);return false;
http://www.policespecials.com/forum/ind ... opic=41091" onclick="window.open(this.href);return false;

To add further confusion, it seems as though similar device (http://www.glow-sticks.org/Drivemocion- ... -Sign.html" onclick="window.open(this.href);return false;) is perfectly legal. I also remember them using one of these signs on and episode of Top Gear when they went on a caravaning holiday (" onclick="window.open(this.href);return false; - 7:02).

A guy at work wanted to know about this to display signs like 'Dont hog the middle lane', 'Put your Headlights on' and 'Stop tailgating' although I'm sure I could be more creative!

Does anyone have a definitive answer for this?

Thanks,

Ash.