Slightly off subject but what would Sanquhar in Scotland have done during the Jacobite rebellions of 1715, and 1745. They would have been in "rebel" territory both times. So presumably Royal mail would not have been operating normally.
Sounds like a once in a lifetime opportunity for a retired or retiring collector wanting to get away from it all and experience running a small post office. Cottage just the right size for a museum or such.
£275,000 is a lot of money in a town where you can buy a house for a third of that, given that there's probably not much money in the business. I suspect some decent subsidy may be needed, unless hoosierboy's eccentric collector comes along.