Long story cut short.
I know someone in the police force and had cause to ring him today to report that two 30mph limit signs had been put on the correct side of a school and the limit for that road reduced from 40 to 30 but the old 40mph signs the other side of the school had been left in place. His reply was "yes we know, it's up to the council to remove those old 40 signs but they just can't afford to, all we can do is request that they do. There's lots of places in Derbyshire like that and the limit is unenforceable if anyone disputes it, there's also a lot of places where the limit signs should be illuminated and either the lights aren't working or have never been fitted in the first place, which again is down to the council, they're also unenforceable should anyone dispute a ticket"
I think the "if anyone disputes it" statement means they are still sending tickets out knowing they could get rolled over in court or "if" anyone is bold enough to dispute them.
Make of that what you will.