There seems to be a similar decision going on in Sussex too. The sensible and efficient use of a joint POLICE/HEMS helicopter in a small area is going to be replaced by a separate HEMS that will cover Sussex and Surrey. It must be more expensive to run separate operations. Then you have the current inability of standalone HEMS to do night HEMS (in practice). I am not directly involved myself, but the bush telegraph says that the Ambulance people want to go back to using the police hele for night time!
I am afraid it is all about empire-building and people wanting their own toys. Particularly true when the Ambulance NHS Trusts involved don't actually pay for the helicopter, but get a charitable trust set up and get the public to pay for it.