I was waiting for somebody to rise to that quote!
It's historical, in England every bank issued it's own note up until the first world war (
see this link). Scotland just continued doing so.
It's only Monopoly money if you aren't used to it. I personally don't like Bank of England notes just because I am not familiar with them. But if somebody hands me one I don't create a big fuss about it.
Sadly they aren't legal tender so we can't force you to accept them, this is because they are 'promise' notes although they do state 'Sterling' on them. The only things which are legal tender are coins (issued by the Royal Mint) and confusingly, the Bank of England one pound note which you abolished. Hey if you don't want our money we will take it elsewhere.
Does your shop accept Euros? I know many big department stores (i.e. M&S) will take them although they don't advertise the fact.