http://www.speedcamerasuk.com/specs.htm
Are they like this?
Coincidentally I was staying in Luton just after christmas. And I do recall the roadworks there. And the average speed cameras. Junction 10 and 11. I used both exits. I used it as a springboard for trips into London with Mrs Lastlid.
Yes. They are closely spaced. But I have seen them in use in many other places in the UK including Scotland, wherever there are extensive roadworks on the motorway or dual carriageways.