If an M3 is the most comfortable car you've ever been in then I can only assume you've spent your life in little crapboxes or serious sports cars.
M3's are many things but super comfortable long distance cruisers isn't one of them really.
Are cars not much more expensive in NI?
Mondeo - Look for a petrol with FSH, don't be put off by higher mileage for the age as most will have spend the miles sitting on the motorway at 80mph not wearing much.