It's always worth watching the railway scenery hobby, particularly if you are a late north Western Europe kind of player. Companies such as Faller, Kibri, Pola and Vollmer produce a wealth of HO (approx 20mm) scenery and buildings (and other scales to boot).
I've used railway buildings as they are detailed and come in several colours within the same kit. Whilst the plastic can be hard to paint, I find it a little of an irony with the growing availability of painted MDF scenery; a very similar product. I've mostly used this kind of scenery for 15mm WWII, as to my eye the size difference is negligible from the average wargaming viewing distance.
I recently bought some storage tanks from E-bay for about £10. A quick undercoat spray, wash, drybrush and weathering powder soon produced something of a wargaming quality. You can see the results in the included two pictures.