A walk along the coastal path between Aberporth and Tresaith highlighted a local commitment to holiday homes based on old railway carriages. ...... http://rogerfarnworth.com/2022/09/16/aberporth-railway-carriage-conversions/
Viewed from the exterior, I would have missed many of these. It appears that some might be in use as tourist type rentals? At least they were not scrapped. I would wonder if some day a few might even be restored to rails again?
I think restoration to be used on railways is unlikely. As you say, they have been altered and extended and are integral to the buildings they are part of. What seems significant historically is just how many of these old coaches ended up on such a short stretch if coastline!