It is all debatable. The H145 cost significantly more than the 135 but gives only a little bit more in lifting ability which then has to be set against the maintenance..... the 135 is new but the 145 is old school, its still certified as a BK117 and requires BK maintenance [BCARS]. Where a (good new) 135 can still be expected to sail through a maintenance in 5 days (if you have PBH intact) the 145 (and several of its competitors) is going to take 2 weeks or more even when new. That messes with the sums when there are few spare airframes around.
I still see the whole drone thing as pie in the sky. Yes a quad copter in the back of a patrol car is a 'good' thing but they are now playing magic tricks and conjuring up a device that is wholly automonous before they invent and test and try such a device. They have not decided whether it should have one or two engines when operating in an urban environment..... let along created a reliable twin engine drone legally able to fly over cities. The whole reason that UK police aviation is expensive was a decision over 40 years ago that police aircraft must have two engines when over urban environments. If that is being rescinded we may as well get rid of all the 135s and go back to the H125 which works perfectly well in the rest of the world - and is cheaper of course. A single engine drone with a dead engine is going to hurt someone. They are doing it quite regularly already. Its OK if it zaps into a a mud hut in Africa (several instances) but when it crashes into a conservatory in Surrey there will be hell to pay. I have yet to be introduced to a twin engine drone that fits on a lamp post - let alone seen one in action. So we wait with bated breath for Norfolk Police to show us their bit of kit.
On another matter raised earlier, high transit speeds of various types, there is not that great a difference between the fast and the slow. Unless the responding unit has to transit for more than 20 minutes (by which time we are told even continuing is pointless) the difference between a H145 and a AW109 is going to be a matter of a minute or so, certainly nothing to get too worried about. The NPAS fixed wing were faster than the helicopters they were supporting but that difference got lost in the taxi run along the runway (and that sort of got hampered when the undercarriage broke on every single airframe).