Not just the Police!
The way you're all talking is that the Police are the only service that needs communications. They are quite primitive in theirs, other than their new penchant for mobile PNC checks, ANPR and other online matters. The big data users are the Ambulance services with their data mobilisation systems, electronic patient report form systems, and telemetry data from their patient monitoring equipment.
The Fire Services can make use of online building mapping, with greater incident information sent to them relating to potential hazards recorded about any given site. Though much of that data could be held offline in the mobile data terminal allowing much faster lookup on-the-fly.
The ESN is due to go live in 2016, BUT that's not all of it, the 700MHz spectrum will be for an exclusive LTE network to cover this sceptred isle, which will be compatible with the networks that are to be built around the world - yes, for once, the plan is a GLOBAL (as much as it can be!) standard for the Emergency Services, such that in the event of a proper disaster, people from one country can arrive in another one, with their own comms kit which will work straight away (roam!) with the ESN in that region.
There's more to this than meets the eye, but the main matter is to get off of Airwave as soon as is practicably possible, it is the millstone around their neck, and something created by the previous government who should have kept it in-house, not farmed out to private organisations / vulture capital companies.
One final couple of shots - the old VHF and UHF networks had much better coverage than even TETRA does, BUT it didn't have the capacity for multiple "conversations", point-to-point calling, and was not secure at all. It was the security issue that sold TETRA to the Home Office, who then forced it on all of the emergency services. Neither the Fire Service, nor the Ambulance services in the UK needed that kind of secure system with the lauded "interoperability", because at no time will a police dispatcher talk to a fire or ambulance crew, or any other combination. It is all done at command level and passed down the chain. And what's more, Fire services still use UHF for BA operations, not TETRA/Airwave. Once again, all about command and control, as well as cost and effectiveness.