Well Sturgeon has thought of that scenario.
https://www.bbc.co.uk/news/uk-scotland-53336489
The move means anyone entering Scotland from Spain or Serbia will have to go into self-isolation even if they travel via an English airport.
Spot-checks are conducted on people who are meant to be in quarantine, and fines can be levied if it is found they are not
Definitely no insurance cover on that scenario for Scots to get their money back I would have thought.