I've recently had a look at some brick and tile from a site in Castleford. There were a couple of brick stamps, and one of them was stamped:
Fortunately, I had a book that might help be identify which company manufactured this brick. The book is Hartleys Brick by Brick, Pot by Pot by David Wilders, 2003, Castleford Press, £10.00. Although I could not match the stamp exactly, there were photos of other stamps, some of which just had H CASTLEFORD on. So the brick is very likely the product of Hartleys of Castleford, and either late 19th to early 20th century in date (from the form of the brick probably 20th century).
I can't remember where I got the book from - suspect it was a flyer in a British Brick Society mailing that brought it to my attention. But the publisher's address is:
8 West View Avenue