With regard to the terminal station issue, I asked when I first joined the thread what was meant by this and used Lowestoft and Bourne End as examples. I was informed that as the station is not a 'through' station, in that there are buffer stops meaning a reversal is required, then it would NOT be valid. Accordingly, stations such as MIA, Hull, Battersby, Inverness are not considered through stations even though they have through services.
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With regard to the 'pick-up/set down' only stations, these I consider to be valid moves as they are shown in the timetable as stops on that service. I recently played Dalmuir - Falkirk High even though Dalmuir is set down only. Accordingly, I would expect that any Scottish sleeper move would require the next stop to be at Carstairs or one in northern England (with the exception of the Fort William sleeper as this is shown to stop at Edinburgh).