We used to use the Ford Galaxy, with rally suspension and brakes. Not much ground clearance, but good and stable for 130+ on motorways. The armoury sat central, with some seats taken out. Lots of room for that 3am snooze as well:~/
It was cost effective because a handful of them were able to cover the whole county, keeping to motorways and arterial roads, in order to put a whole team on plot quick time.
Someone else has the purse strings now, so they use Discoverys. Sound like a tractor and hardly needs the blues and twos 'cos it's so slow. But they don't have to put ARV officers through the advanced car course, so saved dosh. Like paramedics and fire fighters, they set the response time so long that they don't have to rush to meet their targets (listen to me with the manager speek). But the poor Joe who really needs the help RIGHT NOW - well, who cares about him - who on earth is running this world.