if you remove the seats and the belts you're in effect making it a 2 seater so will be tested as such so you'll be fine.
Some time back my car had the rear belts removed, but seats still in position.
removed rear seats + rear belts = win win pass pass MOT
If its not there they cant test it.
Also if your Windscreen has a crack in it that fails, kick the screen out. that way it passes
maybe it fails on the wiper section, but the screen test then passes