I think i know who did it too. We checked on the cctv and a landrover discovery pulls into the space and stays there all the time i'm there - and leaves before me. The height of the marks matches his car bumper. Heres the rub; he's one of our school inspectors - and i've phoned him and while open to negotiation, is adamant it wasnt him. But the damage was not there before i left for work.
Anyway, he let me look at his car today at his work (while he was in a meeting) and the corner of his front bumper looks like its had more rubs than a pompey hooker! Theres no way i can prove the rub on his is new! Even the car park attendant said he must be a terrible driver!
Update, he's just phoned, and while not admitting liability (fair enough) he is willing to talk about the qoutes i'll get to have it fixed. I think he'll find there will be no negotiation...
AAAAAAAAAAAAAAAAAAAAAAAAAAAAGH! rant over, thank you for listening...