Possible English ancestry

[Rena]

How rare was it for English to migrate up to Scotland at this time?

I've come across both American and English in the Scottish census mainly because they were salesmen, or smugglers organising the local illegal whisky sales..  My grandfather (born 1880s in Cambridgeshire) and his brothers travelled 100 miles north  to find work
Additionally coastal villages and towns had plenty of sailors from other parts of the UK and Europe.

In parts of Scotland where there was a textile industry, then you could find Englishmen who had enough money to put their money into a new factory and additionally those  who had knowledge of the new machinery by such people as the inventor Richard Arkwright.

Then there's an earlier generation where a Scottish female married into a (rich?) English family.