Thanks for that, David. Might be a bit too see-through for my purpose. I must however add some hatches along the wall at the back of the tall walkway, as at present there's no explanation as to how the ice gets up there; I'm assuming a conveyor inside the building.
As far as tanks are concerned, the one I wanted to use was too large and fouled rolling stock on the track running to the rear of the Ice Co. However a postal tube, cut in half, provides for two thin tanks which masks the lack of depth in the brickwork. I think Ammonia is used in refrigeration so perhaps that's what is being stored. Will try and post a picture showing the effect of the proposed tanks as soon as I've time to get the camera out again.