Roly, your story on the one year old MG ICE car is only one side of the story.
Nearly every dealership does do their best for the customer, otherwise they get to know about it through Twitter etc.
I would guess the car is a lot older than ONE year and they customer has been abusive to the service desk.
Anything older than one year and its a repair issue. The service dsk is correct, the first port of call is a diagnostic and that always costs about £120 upfront.
The 7 year warranty, that could be body only, I do not know.
What I DO know is that for any warranty, the vehicle must be serviced at the dealership.
My Buddy bought a new Land Rover when he retired. After a year he had to take the vehicle in for its first service…costing £1200. As the Land Rover had only done 3000 miles or so, he declined.
But the dealership said, well, if you do not get the vehicle serviced by us…you will have no warranty….
Basic rule, dont make a judgement based a one-sided story….no matter what they say…