[Arran]

Directly heated cathode tube types like 80s and 45s are fussy about how they are mounted. I don't think that upside down is a problem but you have to be careful about mounting them on their side, or you can end up with the filament drooping over and shorting out against the plate or grid. Some of the G.G Majestic and Rogers Majestic built sets had a clamshell design where the power transformer and rectifier was on the bottom half. It's sort of odd that these upside down mounted tubes did not have some sort of retainer to keep them in the socket like they would have used on a 7 or 9 pin miniature tube in the 1950s or 60s.
Regards
Arran