I'm past the mid-point in planning a first time month long trip in UK for next spring. After a few days touring Isle of Skye in a local rental car I'm thinking that the next move will be to Glasgow (we have friends there to meet up with). Looks like the best option will be to drop the rental car at Armadale, catch the ferry on foot to Mallaig, then take the train on to Glasgow. It looks like the train ride will be particularly scenic. We will have rail passes. Is there somewhere along the route that might be a good candidate for hopping off the train for several hours then catching the next train? I'm fine also with just staying on the train which will be part of the fun for us.
Fort William would be the obvious. There is a 6 hour gap between morning and afternoon trains. So if you didn't come through Glencoe on the way to Skye you could get off at Fort William, then take a bus to Glencoe and back, or maybe a bus (#N42) down Glen Nevis and back for a bit of gentle walking.
Or a bit left field get off the train at the most remote station in the UK (11 miles or so from a public road)- Corrour.
There is a very good cafe there (you can also stay overnight in the Station or the old Signalbox). And some good walking (on a nice day) on the moors towards the old Shooting Lodge- now luxury accommodation. On a dreich day it is wild a place as they get, but still has a raw beauty about it.
Or stay on to Arrochar and Tarbet Station. It's a short walk down to Tarbet Pier on Loch Lomond for a boat trip.
The other alternative is to come over from Armadale later in the morning, do the afternoon wildlife cruise from Mallaig, have lunch, then see the 1st Jacobite steam train leave Mallaig (and the 2nd one arrive) before your 4pm train all the way back to Glasgow.
Depending on time availability you could break the journey for the night at Corrour station, probably the most remote station in Great Britain.
There is also Rannoch Station too if you like isolated! It has a tea room. Mind you 'several hours' might be a bit too long for either Rannoch or Corrour...