Think it's the same train at the end, a Met-Cam, characterised by its windows. Though the actor boarding at the rear does so with first class accommodation behind, at the rear door. Now the train is departing in the same Up direction, towards Yeovil, we have already seen that there was first class at the Yeovil end, and yet Met-Cam 3-car units could not be formed with first at both ends because that would mean no brake, which were only in second class vehicles. I would expect all the scenes to be filmed together. Surprising.
Being a Bristol unit it's a shame that a destination of Taunton was not wound on the front of the unit. Possibly this element of the script was not passed to the railway beforehand. In fact the unit has no destination blind even fitted, as if it had just been transferred from elsewhere, which somehow fits with the few Met-Cam sets coming to the WR around 1980 still in blue livery.
Maiden Newton long had a wrought iron footbridge, but some time in the early 1960s it was replaced by the typical Southern Region pre-fab concrete footbridge seen here, made from the standardised panels produced at the SR concrete works at Exmouth Junction, quite out of keeping with the station building period and giving a misleading Southern air to a classic old GWR (actually originally the Wilts Somerset & Weymouth, or WS&W Railway) station. The Southern was only responsible for the line for about 10 years, 1953 to 63. The local ragstone-faced station buildings are a characteristic of the line - the similar one at Dorchester West was long boarded up but I see recently has become a pizza restaurant!
Remnants of the Bridport bay are just visible on the right in the very last second of the filming as the train departs.
If obtained locally, presumably the driver seen briefly would be from Westbury depot, which covered the line (and the Bridport branch; the crew for this spent half the shift travelling to and fro on the cushions). Now Westbury depot crew had appeared on the screen before, as they crewed the Titfield Thunderbolt back in the 1950s, when they actually spoke and thus were given credits at the end.