Insurance on 5000sq ft store room?

I have recently been looking at a 5000 square foot storage. It will be used primarily to store stock. Most of the stock will likely be labelled onsite and left at the collection point usually by myself but also might be on occasions somebody else. There will be no other works going on. Only loading and unloading stock and on occasions labelling the products. The landlord has valued the building at £800,000, or so. However I think this is the building/infrastructure and not contents/stock. The landlord has asked for a £1250 premium, and I believe this is to cover the buildings only.