you are fairly young though, and might not remember or know that from the 1980s to the mid 2000s there were fuckloads of ITV drama series based around crime and police.
They are allowed to use authentic looking Police vehicles provided they complied with certain conditions (such as not staging crime scenes in big towns or public areas but that meant many were filmed in semi rural areas in the West of England and the North (other than the Bill which had a entire set for this). Rampant free market ideologies also mean that it is surprisingly easy to obtain a lot of authentic Emergency Service uniform and vehicle items on the open market, although some kit does require either authorisation. bear in mind though that the Police, Fire and Ambulance services have many common uniform items and vehicle designs, differing only in base colours.
in recent times swingeing budget cuts throughout the creative media have led to a lot of these shows being cancelled and creative types put out of work. But they still have a fair few pseudo police vehicles left around, so not surprising someone has thought to make good use of them 😉
