Each Force/Constabulary specified mods as they required them: zip in headlining (to access roof lights), suspension/engine mods etc.
Panda Cars (Unit Beat Policing vehicles) would have had minimum mods as they were only for transport, not pursuit, nor even (theoretically) patrol.
Might have had some wiring mods to allow fitment of UHF radios, but fitting would have been by Police workshops and Home Office radio engineers.
(Dave Rumens was a Radio Engineer, but I doubt if he had any experience of Herald Pandas.)
C.