The R44 is a wonderful helicopter with excellent engine off characteristics but an engine failure from a 1000' hover in still wind conditions will offer no glide distance. In fact you loose 300’ to 400' before you gain sufficient forward speed to develop enough potential energy to conduct a safe landing. The area directly below is where you will end up.
Most ENG work is conducted at heights between 750’ & 1000’ at slow speeds in and out of wind i.e. orbits. For built-up areas I believe this profile to be the domain of twin engine helicopters.
Despite contra belief, engines do stop. Emergency landings are also conducted for reasons other than engine malfunctions. If the river Thames offers the only law abiding place to land in the event of a single engine helicopter emergency one has to consider the consequences of alighting into water with or without floats. At best you will go from being a heli to a directionless boat hitting the nearest bridge or barge to at worst becoming an ineffective submarine!
The reduced operating margins of the R44 over a twin squirrel is of great benefit and they do have a place in the video world but personally I would be very uncomfortable flying an R44 in a low level build up area. AS355s undoubtedly offer more performance and safety for me, my cameraman, passengers and people below. On this basis cost should not be compromised.