Thanks Rod. It's puzzling why you and grams can explain the bike storage locations to me but GWR CS's weren't (in 3 separate emails and 2 phone calls), whilst station staff just shrug their shoulders if you ask.
Meanwhile, if anyone has any doubt about the problems these cubicles cause, check this out from my last trip:
I'd got on at Paddington and was the first bike on, so in the inside slot. I go to get my bike out as we approach Bath Spa and find an extremely heavy and large bike on the outer hook....
with a wooden kitchen stool strapped to the pannier rack!! It was well and truly wedged in to the cubicle and it took a LOT of grunting, swearing and physical exertion to manhandle this off the hook and find somewhere to prop it before getting mine out.
All the while people are trying to get past through the vestibule. The owner should consider themselves fortunate I re-hung their bike in a relatively civilised manner and without causing damage to bike or stool!
Just one of the countless miseries to come in future years, no doubt.