Can a shop in England legally refuse a Scottish �10 note?

I am not asking if Scottish notes are legal in England. I know that they are perfectly legal. The question is can a shop refuse them anyway. It just happened to me and they said their reason was because it was too much hle giving them back out again as change. In fact they said it was Blockbuster Video policy to refuse them! Are shopkeepers actually allowed to refuse it and can Blockbuster actually make it a policy to refuse them?