I only found out about this when I tried to buy a book on my Nook and it advised me to visit the Nook website. I know my Nook is registered so I can keep using it for now, but if I want to buy a new book it'll have to be done on the computer and then side-loaded to the Nook, what a faff!
the-digital-reader.com/2016/03/03/bn-to-close-nook-uk-store-will-hand-customers-off-to-sainsbury/