Mmmmm ...
... The Met Police EC145s and having some strategically placed Bambi buckets would surely be more cost effective ...
I would guess that the operating weight of these 145s would be such that the available payload for water would make them pretty much useless for water bombing ...
Removing all the 'Police' Ops gear would be impractical plus you need an available water pick up point reasonably close by ... for realistic practical purposes not a good idea.