I think this might be The Box of Delights. This was a BBC TV series, originally aired in the UK in 1984, and based on a book published in 1935.
From the one-line episode descriptions on Wikipedia, episode 6 seems the most likely:
"Kay is trapped in the dungeons of the Bishop's Palace. Can he locate the magic box before it's too late?"
In this reaction video for episode 6, we see a few clips, some of which certainly show one of the villains involved in evil magic/the occult. This villain appears to be disguised as a clergyman. At 8:44 and various other moments in, we can see him peering down through a barred window at an old man in a dungeon. In a blink-and-you'll-miss-it moment at 7:40, he appears to be entering the dungeon and leaving a group of - his accomplices? - behind.
A YT upload of a radio adaptation lets us hear some dialog, as he threatens to flood the dungeon and kill the prisoner or prisoners. There's definitely at least one young boy held in those dungeons.
TVTropes describes the dungeon as a "drowning pit":
"Drowning Pit: Abner's dungeon is designed with a mechanism to flood it with water from the lake above; he triggers it in the last episode."
The only full episode I can find an online video of is Episode 3 - which doesn't feature anyone trapped in a pit. But note the early-20th-century clothing styles and setting, which this does showcase.
There is a "reaction video" of Episode 1, which includes some clips from the episode itself.
As for the mincemeat... there are certainly quotes involving people being turned into mincemeat, both in the book and TV show. For the book, this Tweet states:
"There is mention of a man putting his father into a meat-mincer on PAGE FIVE. The English, man. Once you get past the tea and manners there are some dark corners."
Neil Gaiman quoted that tweet, and added:
"Warning: DO NOT BUY THE ABRIDGED EDITION. ... It needs to have detectives (or are they?) and the imaginary mincemeat murder in it."
This blog entry confirms a mincemeat quote in the TV adaptation:
"Actually, I was a bit scared of this programme; there was a lot of talk of people being 'scrobbled' and ground into mincemeat (put my best friend right off mince pies, but I’m made of sterner, more sugar-addicted, stuff). "
Louise Jameson played the main female villain in yet another adaptation - this time an audio drama. In this interview she and some other actors allude to the same or another possible mincemeat quote:
Mark: ... We've just done a bit where Sylvia talks about grinding naughty children up into dog biscuits and stuff like that and that has a nice Brothers Grimm feel to it, which is essential.
Have you yet got a favourite moment or a moment that summed up your characters?
Louise: I think the one that Mark quotes earlier where she threatens the little girl with grinding her up and making her dog biscuits.
Mark: It's genius about dog biscuits isn't it? Because it's not just mince meat, it's very plausible!
Louise: It's dry, isn't it, marrow and... So yes, I love that, particularly as she's being sweet a nanosecond before, that wonderful ability to turn on a sixpence like that.
Barnaby: ... Cole Hawlings is magical and fantastic but yes the dog's meat is where I'm at!
There's a Twitter account devoted to the show here.
The book also has a prequel, which featured the same two villains and confirmed that they were part of a coven of witches. From Wikipedia:
"The treasure is also sought by a coven of witches who are seeking it for their own ends. Kay's governess Sylvia Daisy Pouncer is a member of the coven. The witches are led or guided by the wizard Abner Brown."
(Incidentally, for Doctor Who fans... As well as Louise Jameson - who played Leela - in that audio version, the TV show had no less a person than PATRICK TROUGHTON in a major role!)