The LHR Watchman went to Edinburgh if I remember correctly to replace the Marconi S511 hybrid, (Marconi Tx/Rx/Signal Processor and Plessey Aerial and Tower from the AR1. Not sure about other airport radars but probably went to the MOD to keep the military Watchman system servicable as with the demise of Plessey spares became problematic. Also as NATS had the Marconi S511 some of these went to non NATS airports as spares.