D2s don't have headlamp levelling so at MOT time a headlamp levelling or cleaning device inoperative or otherwise obviously defective is a reason for rejection.
My D2 has a headlamp levelling dial - never understood why though as air suspension and associated bits shoud keep everything level regardless of whats on the tow bar.
A discovery has headlamp washers and if on airbags at the rear would keep everything all in check. So it would pass it MOT only thing it would fail on in theory is not having projector headlamps as a discovery uses reflector style headlamps