I've just come back from holiday to find a 20mph zone in force around the local primary school just a little way along my street. The zone is marked with one of these

and the sign incorporates flashing lights - the limit is only effective when the lights flash. As you leave the zone there is a

sign denoting the return to the 30mph limit.
All ok so far? Now the problem:
1. The residential area I live in is already a "20's plenty" zone. On entering from any of the arterial roads surrounding the estate you find signs telling you that "20's plenty". In fact, 20mph is dangerously fast on 75%+ of the roads here due to parked cars limiting road space and visibility/view.
2. The new

zone is usually only safely negotiated at speeds of <10-15 mph, except during a very short period at night, when heady speeds of 20 might be safely achieved.
I am really concerned about the contradictory messages being given out here. The last thing we need is drivers thinking that it's ok to do anywhere near 30mph on the road in question, but the

sign could easily be interpreted as telling drivers that "it's ok to speed up now, the danger has passed"
I'm going to contact the council, but I'm not sure exactly how to explain the problem in a way that'll make them understand. They've obviously introduced the scheme to try to help - how do I convince them that it's a bad idea? I suppose I could try "speed kills"
