Looks like Bedfordshires finest 'Camera Safety' Van to me-they use a plain white one to change the films. They often site their vans where there are fixed camera's. Beeston on the A1-which is a 50 limit has 2 fixed cameras, both in the centre reservation and able to point either way, and I am still always seeing the van there-usually on the Northbound side. Northamptonshire used to do this lots as well-A14 at Kettering they park on the flyover just before you get to a fixed site-double jepardy.
John