Sawney Bean had a massive cave system him and his inbred brood lived in on the coast in the lowlands.
It was near a highway, so they'd pop up, steal valuables, people, and then disappear back into the caves no one knew existed, which made their crimes all the more horrifying and salacious.
Lots of fodder for the penny dreadfuls of the time.
Apparently there's zero historical evidence that this family actually existed, but I know for a fact the caves do.
Maybe not a good source but Dankula has an old video on them.
As far as organized cannibalism, like in OP's example, I can't recall anything past pre-history. Dated 7,000 years ago, the site at Herxheim, Germany, shows evidence of between 500-1000 people killed and eaten. The bones show that they were cooked, fileted, then bashed open for marrow consumption. There's no indication of farms or massive amounts of hunting in the settlement, so the cannibalism was most likely ritualistic in some form. They have found trinkets and tools carved from human bone. Artifacts have been found in the many mass graves indicating people were brought from far away to be eaten.
In fact the word "cannibal" comes from the 1550's Spanish, referring to the natives of the Caribbean and their penchant to eat each other after a battle. In Old English the word was
selfæta.
I remember the story of Vercingetorix of the Guals, who stood at the battle of Alesia against Julius Caeser. They wound up in a weird siege situation, were Caeser was besieging Alesia, but also himself was besieged by a large Guallic army attempting to rescue Vercingetorix and the city. Supposedly, one of Vercingetorix's generals came up to him and explained that the city could only hold out for a short time, but then joked that there were many woman and children in the city. If these women and children were eaten, they could hold out forever against the Romans. Vercingetorix considered this, and then ordered that the women and children be expelled from the city, as surely the Romans would let them go, and maybe create an opening in the Roman lines the Guallic relief force could exploit. Instead, the Romans refused to allow passage and the woman and children of the city died of thirst and starved to death in the no man's land between the city and the Roman siege lines.