I am like you Mrs Raaz, I am totally non plussed at this phrase, it's certainly not some sort of British saying at all, perhaps the fellow was drunk when he said it, it wouldn't surprise me.
I certainly wouldn't go in any chip shop that serves up Brains Mrs Raaz, and neither should you. I do have an old Spanish cook book from the seventies however that includes recipes for Frittered Brains in tomato ketchup and Brains in Béchamel sauce, delicious.
There is some lively conversations when I show the recipes to my guests on a dark evening LOL, but seriously it must have been part of the Spanish diet in the seventies, they would have included it as offal or lights, and served it up for breakfast LOL.
Nothing worse than liver for me thanks.