Property ruined due to water leak

I used Storage Unlimited for 3 months to store my prized belongings whilst between moves. I paid a lot of money to them assuming they kept the property well maintained and safe. I went to move my belonging out of the storage unit only to find that there was a major water leak into my unit and my bed (mattress & base) where completely ruined! Upon reporting this to the facility manager I was informed that it was probably due to the roof tiles and damaged roof. Surely when someone entrusts there belongings to you and there's even a slight chance that there is a leak and their belongs could be in danger of being damaged you notify them to come and inspect their unit to avoid any problems? This unfortunately did NOT happen. I have now been thrown the usual, we have notices and we not liable blah blah blah which is UNACCEPTABLE! They surely have insurance and therefore should do the honourable thing and replace my bed!