Plenty to keep us going there!
I shall do up to and including Merseyrail for now. More later if others have not done them by then.
NT:
BGG Bring
Is that a new station?
And to add some like you asked
ARR - Arram (Northern)
ASK - Askam (Northern)
BRA - Brora (ScotRail)
BYE - Bynea (Arriva Wales)
CGN - Cogan (Arriva Wales)
CNW - Conwy (Arriva Wales)
DLY - Dalry (ScotRail)
DNY - Danby (Northern)
DOL - Dolau (Arriva Wales)
DRI - Drigg (Northern)
ELG - Elgin (ScotRail)
EPS - Epsom (Ups) (Southern)
GMG - Garth (Maesteg line) (Arriva Wales)
GTH - Garth (HoW line) (Arriva Wales)
LRG - Lairg (ScotRail)
LAR - Largs (ScotRail)
LDS - Leeds (Network Rail)
MRR - Morar (ScotRail)
OLT - Olton (although I imagine that most people going there would prefer to tack a B onto the front of the station name) (London Midland)
POR - Porth (Treherbert Line) (Arriva Wales)
RDR - Radyr (Arriva Wales)
ROO - Roose (Cumbria) (Northern)
SYA - Styal (Northern)
TPB - Twerp
(c2c)
TDU - Tondu (Arriva Wales)