Not being from rural England, and not being up on the latest slang, I was amused by this article from the Register that referred to jam rags. If you follow the link, you’ll find a helpful picture, which I will even more helpfully produce below:
I think that the production people were playing a prank on the actors. Unfortunately, when it went out, some people were annoyed about having to see such things on a shopping list chalked on a board on the wall.
However, I presume the makers of feminine hygiene products and Preparation H were delighted at the unusual advertising opportunity.
Nota bene: Emmerdale is a UK TV soap opera set in some unspecified rural area of England.