A level headed article here
on Speed Cameras UK
We're talking about Hadecs 3 cameras, I think.
"The HADECS 3 speed cameras have so far been installed on the M25 in Kent between junctions 5 and 6/7. More locations are planned on a number of other motorways in the UK, including:
‣M1 in Derbyshire and South Yorkshire
‣M3 in Surrey and Hampshire
‣M4/M5 in Somerset
‣M6 around Birmingham
‣M25 junctions 5 to 6/7 Kent
‣M62 in West Yorkshire"
I guess that as they're fixed, a the databases of decent satnav or radar detector will give alerts