Have a read here...
You should be able to find out some information from your local Police website.
Theres an auction place that sells ex-police cars at Witney near Oxford its called west oxfordshire motor auctions,stick it in Google and it should tell you more,i bought an ex-police car from there before and you can save a lotta cash,the nicest ones are the plain cars that CID use but they tend to cost a little more,the ex-patrol cars usually have a few holes in the roof where the blue lights been fitted but these go for a song,all seem to have loadsa miles except the ones from Jersey etc,their site should tell you when the police cars are up
here is one...... but only good for people in scotland or ireland
Wilsons Auctions - UK's Premier Auctioneers - Ireland & Scotland - Car Auctions, Van Auctions, Plant & Machinery Auctions, Liquidation Auctions, Property Auctions, Numberplate Auctions, Antique Auctions, Motorcycle & Quad Auctions, Boat & Caravan Auctions