Personally, if the Scots get independence I'm going to petition for Cumbria to join them.
The mainspring for Scottish independence thinking is not anti-English so much as anti-London, a sentiment I empathise with completely.
My late husband, who was a Scottish dance band leader, maintained that the cultural border between England and Scotland was the river Tyne, not the river Tweed.
That would put Northumberland in Scotland.
Either would suit me.