I have never had that problem, I do, however, will take one or two precautions, like trying to park, not directly in front of anyone's house, but if I can I will only park between cars, never on the end of a row. Also, I never wash my car or hoover it before a trip, I leave it scruffy and dirty in the hope that it looks so bland that no one will really notice it. I will also keep a couple of old newspapers, usually the Mirror, Sun, Mail or Express just lying casually on the passenger seat. Cheap psychology I know, but does it work? I don't know really, but what I do know is, that to date I've never had a problem.
As examples, I left my car like this two years ago on the outskirts of Keswick for seven days, just up and on the main road from the YHA hostel in Ambleside (right hand side, towards Ambleside, by a stone wall) last year for five days and for ten days in Settle, just down the road from Peter's home three years ago. I can't see me bothering again because there is no pleasure whatsoever driving from Portsmouth via the M27, A40, M40 and so on to places such as these. These days I much prefer to go by train. The other problem of course is, if you park anywhere you still have to make your way back, which is not always easy.