Besides the excursion platforms, Weymouth in the 1950s also used the Melcombe Regis platform at the start of the Portland Branch
This was a bit like Burnham, mentioned further up, where a onetime station, now closed, continued to be used for excursions, the tracks there having continued to be used by freight.
Both had excursions from Taunton. We never went on one to Weymouth, regular car trips being done instead, but in very youthful times did one to Burnham, a special steam-hauled non-corridor train which appeared to involve every church group, scouts, etc in the town. To get to Burnham it needed to pull through Highbridge station across the diamond crossing, then push back over the connecting link into the S&D platforms (for which a 412xx appeared to have been sent all the way from Templecombe loco to pilot, opening all the signalboxes along the way as it was a Sunday with no other S&D service), then forward over the crossing again, about a mile to Burnham platform. Same in reverse in the evening. It would probably have been quicker to alight at Highbridge and walk!