Hi,
Passed one of these tonight (first one I've seen) in a residential(ish) area (Queens Road in Manchester) - basically it's a signpost saying "NRSI Accident Reduction zone" on a big signpost with Police logos and a safety camera warning sign.
About 100 yards further on there's a VAS which doesn't look like it's activated yet but I could see the outline of a "20 - SLOW DOWN" (limit is currently 30)
There's a junction about another 100 yards further on which has 2 (grey) redlight cameras on it, and then the zone finishes.
Sounds like a good idea, certainly makes you more aware of hazards rather than having an apparently random safety camera in the middle of nowhere.
The website is
http://www.nrsi.org.uk/index.php
Looks like a very good organisation.