Re: Banks don't typically issue their own currencies
There speaks someone who's never tried to spend a Scottish fiver
Strictly speaking they are not legal tender, even in Scotland.. The only reason that the Scottish banks are allowed to issue the notes in the first place is that they are required to back the currency as a form of promissary note rather legal tender (and the banks are required to have a sufficient amount of GPB in the form of banknotes or gold to cover said promises)
Some places in England will accept them - especially in the English side of border area. Most of the nothern motorway service stations will also accept them. Outside of that most shops won't accept them but you can (usually) exchange them in a local bank (if you can find one).