I wouldn't worry too much, it can be hard sometimes spotting a ned & most people will look at a nice car, i find myself having a peak at nice motors, especially Subarus.
Just do not leave your keys any place remotely near the car when out.
Until you return to the car and find a 'W' reg fiat Bravo that aint seen a sponge since the millenium parked close enough that Twiggy would find it hard getting out of the door.
Agree with the above park far away AND over 2 spaces
Doesnt cost that much tbh and as said above its only a tenner, nothing really.
Being a paid member of the SIDC gets loads of benefits, discounts, true grip mag
Plus i like warm fuzzy feelings