I would nominate Tyndrum Lower and Upper Tyndrum. They are on different lines, Oban & Fort William, however. According to good old Wiki:- "separated physically by only a few hundred yards, but about ten miles apart by rail".
Tyndrum must certainly be pretty close to being the smallest place in UK▸ to have two railway stations.....................unless someone knows better !
damn you !!!! im going to be up all night reading about the West Highland Line,
interesting fact Most trains currently serving Fort William and Oban split or join at Crianlarich, with the result that separate trains both heading in the same direction generally call at Tyndrum's two stations at about the same time
good old wickipedia