Robin,
I was under the impression that the majority of aircraft do now squawk, including Her Majesties finest (apart from the UAVs of course...). The squawk, whilst useful for TCAS, would also give any ATC/AWACS a heads-up. It's not a panacea for all theatres, but it would be a powerful tool.
I hadn't thought of it being so close to home either. The idea of Swindonian plods aviating drones around the airspace between Brize, Lyneham and Oxford isn't a pleasant one.