To respond to a couple of points here...
The siting of ANPR checks is intelligence-based and well thought out. I can see the rationale of parking in dodgy area but primarily the reason for siting on major routes is volume of traffic and, therefore, hits. This makes the units more efficient by letting them pick and choose the more serious "hits".
In the main the sites are based on main roads with few side turnings in the locality, pinch points if you will, to prevent people avoiding them. For this reason the middle of large housing estates do not fit the bill!
Even without the operation-based sites with vans and intercept cars, most traffic cars now have ANPR on when roving around, which mops up the stragglers...
In response to Sp!ke's point about Slovenian registration, I suspect your tongue was at least partly in cheek but this isn't recommended. If you are stopped for a serious enough offence then the only other option is arrest if you can or will not produce a British address.
Asides from that PNC has the capacity to hold intelligence markers, if placed, on ANY registration mark. If it came to light that someone was using a foreign registration as a ploy then it may well be flagged against that plate and you would be tracked down anyway!
Fully fully accept the points about "Motoring underclass" though. Rest assured that the new powers of seizure for uninsured/licenced cars are starting to have an effect and, anecdotally at least, the number of "pool" cars are starting to decline rapidly.