Here are some STLs representing a GWR style buffer stop. Currently two have been uploaded, they are identical other than the one having wooden type buffer beam and the other representing an rail beam.

I have printed these upright in one piece in PETG and other than the support being a bit tricky to remove from between the guard rails they printed fine.

Like many buffer stops there seem to have been many variations on a theme.

For the rivet counters, the chairs are not GWR style but are BR 1948 style. These have been used as openSCAD is not ideal for creating fairly organic shapes like a rail chair. Instead I've used a modified version of a model from thingiverse.

https://www.thingiverse.com/thing:2886302 Thanks to davedix for sharing.