Vehicle Damaged

I recently booked with Purple Parking for Manchester Airport parking. The car parking was with DMD at Styall Rd.
I have a motorhome and this site said they took them for an extra £10 a week payable on arrival. On arrival they tried to charge me £15 but as it was clearly stated on the Purple Parking paper work they honoured this.
In honesty the shuttle service to and from the airport was fine and was it not for the fact my vehicle had a big scratch down the side when picking it up I would have been giving this review top marks. However, the sign of a good company is how they rectify problems and here is the failing with DMD. They refuse to admit liability. I was told all vehicles are photo scanned on entry which I was happy about as it would prove my case. Despite requests they have not given me the photo evidence and state that under the terms and conditions vehicles are left at owners risk. Originally I complained through DMD. I have now contacted Purple Parking and I am awaiting a response. If you do use this carpark learn from me - take pics of your vehicle before leaving it and a note of your mileage. I am most annoyed about their attitude of making me out to be a liar.