Devil & TPP - you both make most valid points, at the end of the day the public purse is paying for what?
Once the accident's happened, and it's been fairly comprehensively determined that the aircraft systems are not significantly at fault (and that any potential system faults have already, and fairly immediately, been addressed by extra operational &/or maintenance procedures, as they have in this case), does it really make any difference if the report appears 12 or 18 months after the event?
Fitting CVRs to all aircraft, including C150s etc, would be the icing on the cake, but I'd suggest compulsory mode C transponders would come far higher up the priority list, for every day benefit, from a safety point of view. Police aircraft in the UK have an excellent safety record, especially given the hours, weather conditions and endlessly flexible tasking flown.
Suggest CVRs if you like, but concentrate on what's done well and ensure best practice is shared. The current modus operandi does not require a knee-jerk, health & safety driven, sledgehammer - the nut doesn't need cracking, though it might benefit from a little polish!