Can I still be puzzled? ('The more I find out, the less I know' - not just a pop song but philosophy!)
With the low cost of digital photos, I now take a lot - perhaps making up for steam days, when I regret taking so few because of cost.
Anyway, here's some interiors of the ex GC sets.
First, a TRFB. It's ex Great Western, and undoubtedly has lift up armrests but of course no lavatory.
View attachment 73866
Next, the TFO, re-trimmed but otherwise in GC condition (they were converted from loco-hauled). I can't be certain, but those armrests don't look like they lift up - looks like they would jam in the seat side if they did.
View attachment 73867
And here's the lavatory in the TFO.
View attachment 73868
I can't see that there much more PRM - y than the EMR home sets, to be honest, and certainly less so than the LNER sets. Sorry I haven't got any Standard photos but, to avoid any debate, I never take interior photos where an identifiable person would be included.