depends
my little brother is a a PC with a force in the midlands, he's past half way through his probation
from near enough day one he has been able o drive police vehicles, marked and unmarked, but not allowed to use the blues in motion or claim exemptions - nearly everyone with a driving licence has this authorisation in the force he works for
at sone point in the next few months at or around the time he completes his probation he's been told that barring major chickenups on his behalf he'll be sent on a 'response' course which will let him drive the beat cars on blues and twos and claim exemptions, sometimes these courses allow the use of larger cars as well ( they have a few mondeos and larger engined petrol versiosn of the beat cars as well as the normal beat cars which IIRC are TDs) - a good proprtion of the non probationers have this
then there's the long queue to get on a clbutt one course - the course that traffic, firearms on ARVs , and drivers of the 'big' area cars have to do outside the functional specialist units only a relatively small propertion of officers have this - to the point where the vehicle (usually a Volvo estate) goes uncrewed some shifts because there isn't a driver available
