"The Spanish have no issues with homeowners arriving to attend to our properties and neither have the French if you are in transit through the country and you have a valid negative test."
I think they do hence it not currently being a valid reason to enter Spain - although some are getting away with it. France is slightly different, hence travelling via France is probably more likely to be successful.
"It’s the restrictions of the English government that are causing the problems."
These restrictions do in fact allow you to leave for the purposes of purchase/sale/preparation of rental of a property!