When Lancs were making their original bid for their 355, they worked out that in real terms, running the helo post purchase woudl be no dearer than keeping a double crewed traffic car on the road 24 hrs a day 365 per year.
I have never had the time to actually carry out the exercise, but think research should be done into low cost air support. There will always have to be a main helo (135, 902 et al) but I think there is a case for the additional use of the likes of the R22 and maybe even auto gyro's?
The biggest difficulty is funding. Every request for a sortie has to be carefully assessed by the pilot and observers, and a cost/benefit analysis carried out on the hoof. Money only goes so far and thus prevents the aircraft patrolling as such. However, I believe the Met do fly, or used to fly, some sort of patrol.
headsethair
The London Fire service did trial a BK 117 back around 1995. It had little thunderbird pods to put in the back
I personally beieve that joint services machines are worth a look. Going up to the size of a 365 offers huge possibilities from SAR to medevac to customs to police.