I think this idea may actually have some merit to it. Of course, I'm not really full-bottle on how you lads do things over there RE:your Police force and whether they're actually any good or not but I know over here that we're experiencing some severe manning problems and the privatization of a few things the Police currently do would free up blokes to do some srs Policing. (With a 20% cut however this is starting to look pretty stupid...)
Of course that accountability thing is a strong one to consider. I'm not aware of the peculiarities of UK law but at least under Aus law anyone privately employed in a security role can't do a lot more than place you under citizen's arrest and are certainly nowhere near free enough to consider actual Police duties in the slightest. Though the fact they're being employed to watch neighborhoods make me think your law is a fair bit more lax in that respect.
Each county has its own police force which is subdivided into divisions, though a division generally covers a wider area than in the states as I understand it, there is no umbrella force like the FBI but the London Metropolitan police often takes on this role where needed.
The police as it is does a good job, there are a few issues with miss conduct but these are rarely press worthy and cases get solved. the main issue with law and order is that the courts cant do jack because the prisons are too full so they have to rely a lot on fines, tagging and community orders for the most part.
Except in the cities crime tends to be drugs, burglary and domestic violence. For eyes on the street stuff we have the Police Special Constables who are civilians with limited training who work on a part time basis to supplement the police, though government funding for them has been cut as well as the main police.
All this comes down to is the government trying to save themselves money, and tbh privatisation of services that retain the kind of government input that this will require rarely saves the government much money and usually degrades services, just look at our rail network for an example of this.
