Just a couple of additional points from me:
1. It's just not the police that are exempt from the rules on using mobile telephone when, instead, they use two-way radios.
If Joe Bloggs buys a pair of walkie-talkies from Maplin's and then uses them to communicate with his Aunt Ethel (in a following car) as he drives down a motorway, he (and Aunt Ethel) can't be prosecuted under the legislation relating to the use of mobile phones. (However it's possible that they might still be prosecuted for not being in full control of their vehicles, as users of mobile phones always could be before the current legislation came into force anyway - assuming that the police and the CPS could actually prove it).
2. NJ writes: "There are remarkably few accidents involving police vehicles".
Possibly that needs "that we get told about" added onto the end of it!
I used to deliver car parts to the vehicle workshop at Suffolk Police's HQ, often calling there several times per week. Nearly every time I visited there was a newly-pranged vehicle (or sometime several) awaiting repair!