1. Mallaig NW Scotland 2. Dartmouth/Kingswear - South Devon 3. Acle - Norfolk Broads Acle is the most odd as you feel it just should not be there, quick stroll and you are on the broads
Bempton in NE a close 4th fyi - a very ghostly place with an abandoned raf field to the north of the station
Not sure what you mean by most remote but for me, it was Hel in northern Poland. don't know about places 2 and 3.
Dartmouth/Kingswear - amended There is a faux station at Dartmouth but you are right, Kingswear is the last stop