Just read this from another web site. Might be usefull to know.
"I know that if you are not speeding this is not an issue, but for those who do cruise along with everyone else on the motorway this might be of interest:-
I have just been informed by someone who knows someone who works for the Metropolitan Police Service that as and from the 15th February 08 all the Speed Cameras in the Variable Speed Limit section of the M25 near Heathrow Airport (JCT 10-15) are going Digital and the activation limit is being lowered.
They are currently the older film type cameras and Set at 90mph when the Variable Limit Signs are not in operation.
The new digital cameras are going to be set at the normal 10% 0f the speed limit + 2mph (80mph + and your taking a risk basically) when the signs are not in use i.e. national speed limit. I can�t confirm the activation limit when the signs are set (variable limits showing) but belief it would be the same 10% + 2mph of the speed shown by the sign at that time.
Please pass this on to anyone you know.
I hope this saves a few of you getting points on your licence!!!"
Ex77