When I was young (haha, long time ago) very posh people would only say 'lavatory' not 'toilet'. So one used 'lavatory paper'.
'Toilet paper' was a bit lower middle.
The words 'loo' and 'loo paper' were for the lower classes.
'Bog paper' was for the lowest of the low.
The class system/snobbery in UK was alive and well then.