I had a Focus RS a few years back that had to be parked on the road outside my house and obviously attracted a bit of attention. I had a ghost immobiliser fitted which at the time were one of the best . Not cheap though , I think it was about £400 at the time. Also as a visual deterrent I had a disc lock on the steering wheel , a lock that fitted over the hand brake and around the gearstick ( had this in the shed from the late 80s ) and a wheel clamp . Was a bit of a faff putting it all on or off but did the trick . Also had one of my security cameras pointing at it . Had plenty folk mooching around it over the 2 years I owned it but no one attempted to take it .