Being from the Southern UK, and speaking RP (received pronounciation) I would be rather surprized to hear a non-Yorkshireman use ‘our’ and ‘your’ when referring to family.
You are right that CUA is basing a lot of its humour on a ‘class’ thing, but the joke is that Hyacinth gets it wrong - you get similar humour in Minder where Arthur Daley persistently uses the wrong words or pronounciation.
Or Del Boy
Would you really? Or do you just mean that you can’t tell one northerner from another? 
I’ve noticed that Hyacinth always says “my sister Daisy” or “my sister Violet, the one with a sauna and room for a pony” instead of “our Daisy.”
I’ve found the “our John” construction useful when in conversations in which the participants might be referring to any one of several persons named John, but it’s not a common usage.
It’s used here in Nottingham, along with ‘our kid’ (well, ‘arkid’) to refer to a brother.
As a Yorkshireman I’m surprised to see our FRDE spelling surprised surprized.
I’ve lived in Yorkshire all my life and in my experience usage of “our” and “your” isn’t very common. You do hear it from time to time and nobody seems confused when it is used but it isn’t the norm. The usage I hear most frequently is “our kid” and “your kid” to refer to a brother.
OED versus the Cambridge version - check ‘realize’.
To me ‘ize’ makes more sense, so I generally use it, standardization in the absence of a definitive Dueden.
Admittedly the true standards are erratic, but I prefer to be consistent.
Heck, Chez, I thought you conducted your morbid experiments in Stow, a migratory Yorkshireman, how interesting. Or is there a Stow in Yorkshire, I did not find one, but my search was cursory (Cab Sauv impedes my Googling).
Just joshing FRDE.
There’s an Americanism for you just to illustrate my international linguistic credentials. My home is Stow in Gloucestershire and I don’t think there is a place of that name in Yorkshire. I was thrown out of that illustrious county because of the morbid experiments you mention.
I think I’ve since been sentenced to death in my absence.
I’ve heard people Liverpool Manchester and Lancashire use it. It’s more of a working class thing, and probably why Hyacinth doesn’t.
Until today I thought Stow-in-the-Wold
I found various Stow Hotels in Yorkshire.
I think the odious suit might be down to smells being either oil or water carried.
Wool would disintegrate without oils, so dry cleaning needs to be a compromise.
Sure, that’s the one. Stow-on-the-Wold (Stow for short) west of Oxford, east of Cheltenham and south of Stratford.
Back to the OP, the Mafia also uses the expression our as in Cosa Nostra (Our Thing).
Regarding the suit, you must be talking about my other threads.
According to reliable sources the death sentence only applies if you attempt to return
It’s not common in Scotland, with the caveat that, for all I know, it might have been common in Dundee at whatever point in the Dark Ages that comic strip started. Like others posting here, I tend to think of it as a northern (vaguely defined) English usage.
I’m from Wigan, Gtr Manchester (not Yorkshire!) and it’s used all the time. I’d hardly call it a “working class” thing.
Born and raised in Yorkshire. I’ve heard it used frequently. I don’t use it myself though. For some reason I find it really annoying.
My aged mother lives close to Stow - it keeps me away from the area.
It seems the ‘our’ thing is more widely used than I expected.
Nice pun on the ‘Threads’ 