LED sidelights should be ok as long as they are white, and not blue.
As for Xenons, if the car is not fitted with them from the factory, whilst fitting is pretty easy, an MOT wont be.
Fitting them to non projector lenses gives a lot of "bleed" and you dont get a good beam pattern, with Xenons, you also need a self leveling system, and headlight washers, both are tricky to retro fit.
Beam pattern (has always been part of the MOT, as has the headlight aim) but if you have xenons, the tester should check the usual headlight height adjuster - tumbler type switch is not present as there is a self adjuster, and they should also check the operation of the headlight washer system.
What If There Were No Hypothetical Questions?