I dont know if this is happening country wide but in birmingham the council has been quietly changing speed limits down from 40mph to 30mph, I say quietly because there are no waing signs and the only clue is that all the 40mph signs have been removed.
this is happening on quite a grand scale now as lots and lots of roads in the city have changed to 30mph zones, I have only found out via an mp's blog and word of mouth, I dont mind this if they put new speed limit signs up, especially near the speed camera's!
Urban roads are always a 30 limit unless there is a sign to say there is a higher limit so there is no need to put up '30' signs. There should however be a 30 sign at the start of the speed restricted area on all roads, extra signs are not mandatory.
Suffolk has reduced the speed limit on all roads passing through populated areas to a maximum of 30mph. Many parts of the county now have 20mph limits in town centres and on housing estates.