Has anybody ever been fined or prosecuted for exceeding the 20mph limit. Seems to be largely ignored to me. (even more ignored than the 30 limit). May be it slows some up from 40 to 30.
Apart from in Royal Parks I'm not aware of it. In my experience compliance tends to have a mild link to how big the area is - contrary to what the ranters say it's always been the shorter sections of road that don't have compliance and bigger ones that do. The ranters and ravers often claim it's the other way round and use this as justification for no more 20mph limits!