Heared this term twice in episodes I have seen in last few weeks watching Up Down. First was when Hudson is referred to as a confirmed batchelor by Georgina (IN Lily's last episode)
The 2nd was the explicit episode with Robert Hardy playing a gay chap.
Richard and James had a conversation about Sir Guy (Hardy) where they said things about him that were never said about Hudson--He's a "safe" man (to have around your wife). And James gives a knowing nod.
So I don't think the term confirmed bachelor necessarily implies being gay, same as "spinster" doesn't necessarily mean an aging lesbian. Of course it might, but it depends on the specific case. There is nothing in the show to imply Hudson being gay, so I don't think Georgina was implying that. Hudson was "married" to his job, as I suppose many servants were.
It is a shame the series never explored how much the servant life could deprive butlers of "normal" relationships and happiness through marriage. To some extent the loss of all that for women was explored through Rose (who had a chance to escape, but had a kind of Stockholm syndrome for life in service and feared leaving its security), but not really with men (let's not mention the bizarre "Disillusion"!). I reckon Hudson was so uptight because all he had was his job and reputation for being one of the best in the business.
Would it have been "look-the-other-way" acceptable for an unmarried upper-middle class bachelor to have discreetly visited courtesans or had a "kept" woman?
If she thought Hudson was gay then her gaydar was as bad as Elizabeth's. He was devoted to his work and his own reputation. He fell in love with that young maid(don't remember her name). The only reason he ended it was his sense of propriety. I found that to be very tragic for him. He resolved to make the best of it with Mrs. Bridges in the end, again because it was the proper thing to do.
I don't recall it ever being mentioned that Hudson ever had any love interest, except for that episode (Lily). You may be thinking of Rose--who mentions in Episode 1 that she was engaged but he died in the war in Africa (presumably one of the Boer Wars).
It's been ages since I read some of those. There were the novelizations of Seasons 1-4 (I read the first three) and the "backstory" books of which I only recall reading the one about Richard Bellamy. I really should get around to the ones about Hudson, Rose, Sarah, and Mrs. Bridges.