This. They'll probably put an advisory if seat belts are still there, but to be honest, they shouldn't test if the seats aren't there. I had the rear seats removed my Peugeot because it was in between jobs, and there was nothing noted.Be sure to do the seatbelts too though. Some testers get funny about there being no rear seats but still seatbelts intact.
That was a bmx LeeIve turned up before without a car and passed mot. Just saying.