actually both those linked are lift bills, the UK one sheet is VERY ugly. (though i do have one)
Hard to say re value, its probably a movie fondly remembered by some older Brits, but I dont think anyone outside UK would care about it (except a few freaks like me).
I think they are over priced, but the cheaper of the 2 sold by Greg Edwards (rarefilmposters), well he is a good seller and knows his stuff. He is probably on the mark.
I saw the film as a youngster and always loved it.