If the taxi driver doesn't want to accept Scottish bank notes, he doesn't have to. He is not obliged to accept any form of currency, in truth.
Since (presumably) the journey is over, he can insist that I pay my debt in legal tender - but not on the spot: legal tender is for when it reaches court. So, I would tell him that he can take my Scottish money or invoice me.
Since (presumably) the journey is over, he can insist that I pay my debt in legal tender - but not on the spot: legal tender is for when it reaches court. So, I would tell him that he can take my Scottish money or invoice me.