I found however that none would really fit the bill, and would need significant kit bashing to fit in the space I had planned for it.
It is at an angle and therefore the building, when viewed from the top would need to be largely triangular. I therefore decided to scratch build my own warehouse. It is entirely 'made up', I don't have a specific prototype for it, but I will make sure it will look 'authentic' enough not to look unrealistic. Besides, I had several scrap bits of styrene laying about that I could use.
Here are some progress pictures. This evening I've spend extending the structure , added a door and steps , re-enforced the inside of the walls and added a ledge on which the roof can be put down, and put a loading floor inside behind the doors. This will enable me to add a small amount of interior details that might be visible where the doors will be modeled open, but not the complete depth of the building.
Koos

Scratch build warehouse by K2K Koos, on Flickr

Warehouse build by K2K Koos, on Flickr