The original poster questioned why the one existing training location was at Paddington, rather than somewhere more 'central' to the
FGW▸ area - such as Swindon (operated by FGW) or Bristol Temple Meads (oprated by FGW). Several subsequent members of FGW staff posted in support of that challenge.
However, I'm not FGW staff, so I'm perhaps not qualified to comment.
what % of FGW staff are based in Swindon/Reading/London/Oxford/south wales/Bristol - in which case day trips are feasible and hence no hotel requirement. FGW might have control centre at Swindon but to the general public they run paddington - that is their flagship so to speak.
Plymouth/west staff, even at swindon I would guess, would have to still take half a day and overnight.
Property costs would have been less maybe, but ...
Do FGW use that centre at Paddington for more than just staff training? Meetings with the gubbermint? etc etc
There is a reason a lot of companies still have a head office/meeting centre in London rather than more conveniently and cheaper located else where - its because its still a form of status symbol to have such facility in London