I'm sure you'll find on TM that every owner of a new Morgan goes through a process for fettling and generally this can only be done with use of the car. Very low mileage examples are unlikely to have been fettled so you should be prepared for having to accept some additional costs in early ownership especially if out of warranty.
Agree with John - Aero 8's are better when used and maintained (like all cars). Low mileage cars, which haven't been used and maintained properly, could (will?) suffer with niggles (due to not being fettled when new) and issues created by lack of use.
I may know of an S4 for sale - that isn't currently advertised - but I believe it is above your stated budget.
