Probably the fact that Black Friday is an American phenomenon that is successfully exported to mainly Anglo countries. Doesn't impact mainland Europe as much.

Black friday is not small in europe. We (germany) have BF ads all around.

I don't see how Brexit could be part of the reason. Unless the economy is so bad more people are determined to find a bargain.

There's more Black Friday marketing in Britain than some other European countries, and maybe more use of an American credit card based shopping platform.

There should be a something similar to Godwin's law but for any discussion about UK. The longer the thread the more likely someone will mention Brexit.