You would'nt be able to do anything, due to the sign that will be with out doubt screwed to a wall in the carpark somewhere that states 'owners cars left at their own risk'. I find the same problem whilst Im out shopping at Harrods ....it seems to attract some of the regular Sainsburys shopping chav scum at christmas, some of them dont even have their own staff to push the trolly for them...they parade around the place dress in some rather obscure atire that they proberbly bought off a 'geeza in a pub', it really lowers the tone of the whole shopping experience. In fact next time something like this happens i will endevor to drive straight home, log into Passionford and tell you all about it