There's a Preston about 1km east os Ellingham, found on Bing Maps (OS). Pretty small but Preston Mains and Preston Smithy are named. No reason why there might not be a mill thereabouts
The 1900 25-inch map of the area (online) shows Preston Tower with a few buildings, one labelled Engine Shed (no railway anywhere near!) but no evidence of a mill or any significant stream to run a watermill. I guess there may have been a windmill, or perhaps it is referring to the engine shed?
