I was pointed to this via a Dutch pirate radio site, as Agentschap Telecom is upgrading their similar system (so it can also send data to the tracking vehicles). This is a trade/sales video from Agilent (formerly the electronics division of Hewlett Packard, now being rebranded as Keysight); who make a lot of RF test equipment. They had a big factory/lab in Scotland, although much of this has moved to Penang in Malaysia. It was uploaded to youtube in 2011, although the data shown is from 2009. If you find the description of the theory a bit heavy (it does go on for a bit although worth watching even at a later date as it explains in fairly simple terms how radio signals are geolocated) fast forward to 2:54, where you will see where the demo installation was set up, and what frequencies they are monitoring; I can understand why they picked those locations.. :laugh_at:

These days Ofcom rarely take down a TX in London unless it is causing bad intereference to another licensed broadcaster or wrong signals on aircraft frequencies; they are smart enough now to realise it will only get replaced, often with unpleasant traps such as exposed live 230V wires, sharps and all sorts else (pirates don’t always know or care if its Ofcom or another rival station); they just gather evidence on them and pass the info to metpol who check out if there is any other serious crime involved; if so they go in hard with trojan (armed) units.

I expect similar installations are around most large cities and probably here as well (they would also be used to check for interference that can cause problems to aviation and maritime communications)