Nothing is more destructive to a vehicle than being stood.
Maybe not 'nothing', but I agree with the sentiment.
Diesels are designed to do miles. Being stood or do lots of short journeys is not good for any car and potentially very damaging for a diesel engine, and negates the economic benefits of having one.
Personally if I was shopping for a diesel (which incidentally I hope never to do again) I would be looking for a minimum of 6k per year with a target of 8-10kpa.
Tidy, low mileage MGRs are getting rarer and there is a gulf starting to open between these (usually £3K+) and the more average examples (£500-1500). Spending more on a low mile minter makes more sense if you intend to keep the car as a cherished future classic than using it as a daily hack imo.