The rule change relates to restricted roads - those with a system of street lighting where street lamps are no more than 198 yards apart. Up until now, the general rules have been that there is a default 30mph speed limit unless another speed limit has been passed by the local authority and is shown by regular repeater speed signs.
As you say, national legislation in Wales was passed about 18 months ago and has now changed the default limit there to 20mph where you see this system of street lighting and no other repeater signs. It is open to the local Welsh authority to pass a local speed limit putting it back to 30mph (or other) on local streets.
Quite a few local authorities in England have already made local orders covering local areas (some in the SW come to mind), where you will see general 20mph limits (not just on various roads). So, while there is no general push for a national change in England, it is occurring in various areas separately, where there is a demand for it.