Today i took a trip to my local timber merchants and on returning to my car found that a large fence panel had fallen over and hit my car

, picking the fence panel up revealed a large dent and some large scratches to the wing of my car

, i went back into the shop to tell them behind the counter (one of the staff actually saw it hit my car) and they gave me the bosses number as he wasn't in, one of the other staff then told me that the same panel had fallen over in the morning and damaged one of their vans

(someone just propped the panel back up again and then it fell over and damaged mine

)
what i want to know is do i have a case for claiming for damage against the company or will i have to get it reapired myself, there are no 'leave car at your own risk' signs in the car park or anything like that, i wouldn't mind too much but my car hasn't got a scratch on it apart from this and it will significantly de-value the car

PLEASE HELP