I read this one in the early-to-mid 1980s, and I'm fairly certain that was when it was written.
The protagonist is a middle-class-type who has recently lost everything. He has no job, has lost his home, and so on. He may also be drinking heavily at this point. One night, he happens upon a group of homeless men and women sitting around a fire. They invite him to join them.
As they exchange dialogue, the homeless people talk about how polite society has turned their back on them, and they live by their own rules now. The protagonist begins to feel a kinship with them. IIRC, there is a leader of the group, who keeps passing around a bottle of red wine to his fellow homeless people. The light from the fire is dim enough that their faces are somewhat covered in shadow.
Near the end of the story, they hand the bottle of red wine to the protagonist. The protagonist takes a draught from the bottle, and instantly gags. There is a line that goes something like "thick and salty..it was NOT wine." The bottle is, in fact, filled with human blood. The man also sees their faces clearly for the first time, and sees they are all horribly scarred with burns.
The group of homeless people reveal their secret in the fire. There is some sort of malevolent spirit in the flames, who is their 'protector', in exchange for their service and the price of being burned horribly. The protagonist has reached the point where he too, has turned his back on society. He leans into the fire, and allows the spirit to claw at his face with flaming talons or the like. After it's finished, they toss him a piece of (human) meat, after which there is a line something like "it tasted just like venison...somehow he always knew it would."
The store closes with the protagonist briefly sharing a tale of them catching a jogger for "dinner" and throwing her bones into the Thames.