A while back I posted a photo of a quite delightful fuel tank near Stoke Mandeville. Swinging the camera to the left brings up these 1970s offices. Still in use, but looking a little worse for wear. The concrete pad to the right is the drip area for the fuel tank - or could it have been a weighbridge at some point? Most people will now buy a ready to plonk item for this sort of thing, but a few selected and altered bits of Ratio and Wills should sort most of it out in this low-relief scenario topped with some wet and dry for the felt roofing.