Can't speak for UK but you can get absolute big reductions here in Oz on the black friday sale.
Noticing that many people in UK are anti anything American, actually Halloween was exported to America from Irish English and Scottish immigrants nineteenth century so it's not a yank import at all.
TV shows are now mainly American.
Films of course are, especially the ones that re-write history. They love them.
Halloween was celebrated in the UK in the 60's. Your mam bought a turnip/swede ? hollowed it out (and used it for your tea) carved a scary face out, stuck a candle in it and that was your Halloween.
Thanks to the yanks, it's now a multi million dollar business that lasts weeks.
Yes we are getting sick of being Americanised.
Black Friday is part of that americanisation.
Over here you rarely get a good deal in a sale, it's just promoted that you do.
Have I mentioned we are sick of the Yanks ?