HID without self leveling etc WILL fail the MOT if it MOT done properly.
But how is an MOT tester supposed to test/check this? Stick a load of bricks in the boot and see if the headlamps dip?
Then there's actually identifying a car with aftermarket HIDs in the first place; Some peoples installations are very tidy, to the point you wouldn't even see anything under the bonnet, and I'm pretty damn sure that a tester saying 'it looks like HIDs' when they power the headlamps up wouldn't suffice.
As long as the beam pattern is correct, you'll have a pass, which is precisely why I'll be leaving my HID kit installed for its MOT in two weeks time.
The problem you'd have if
an MOT was to go into this much detail is the cost and time it'd take, because if you were testing things like this, you'd also have to check the powerwash bottle is full, and test the light output
as well as the beam pattern before and after a cleaning cycle. If it was an OEM system, are they also going to check that the washer bottle has enough capacity to do the minimum 25 cleaning cycles required by ECE regs? Where would it end?