3 carriage 144.
Remove a row of seats from every carriage and move the rest down a bit. Also install seat back and window tables.
MML HST
Refresh seat coverings where necessary. That is all.
I disagree! The MML ones are the worst HSTs, besides the ex GC ones
EMT HST
Strip out the whole interior!
Repaint and replace all of the toilets
New Carpets, new luggage racks.
Replace lights with a warmer colour.
Replace the first class seats, with the GWR ones, with a real leather covering
Refresh standard class seats with leather headrests, like TPE.
Add plug sockets, and replace table top coverings with wood effect.
Basically turning cheap and nasty Stagecoach into a premium Abellio/First interior.
ex GC HST
Same as above, but add a ton of addtional seats, and get rid of the ghastly carpet on the walls!