No the police don't pay, neither do these others:


(2) A toll order shall contain provision exempting from liability to pay any toll—

(a) a police vehicle, identifiable as such by writing or markings on it or otherwise by its appearance, if being used for police purposes;

(b) an ambulance as defined in section 4(2) of the [1971 c. 10.] Vehicles (Excise) Act 1971;

(c) a fire engine as so defined;

(d) a vehicle exempt from duty under that Act by virtue of—

section 4(1)(g) of that Act (invalid carriages),
section 4(1)(kb) of that Act (vehicles used for carriage of disabled persons by recognised bodies), or
section 7(2) of that Act (vehicles used by or for purposes of disabled person).