My other car has developed an ABS fault at the moment, it's still perfectly legal to drive but won't pass the MoT as it is unless i jerry-rig the ABS light to the SRS light. Alternatively i could just fix the problem but that might be easier said than done given it won't let me read the codes. Sort of suggest the ABS ECU is belly-up but that's for another forum maybe.
Likewise there is (or at least wasn't last time i checked) nothing in the C&U about the light source - the moving traffic offence would be dazzling oncoming motorists if the LED bulbs gave an incorrect beam pattern but having them fitted isn't illegal. They won't pass the MoT because of a govt knee-jerk reaction to the mass influx of cheap Chinese LED headlamp bulbs that simply have a large COB LED that gives no definite point of light source, just a huge blob of light that gets refelected all round the refelctor including in the areas where there shouldn't be any light.
Most MoT testers tend to turn a blind eye to LED headlamp bulbs as long as the beam pattern is correct knowing full well that if they insist on filament bulbs being present for a pass, i'll simply swap them back after the pass certificate is given, as would most other people.
I would guess their mindset is they'd rather test it as being safe with the bulbs they know i'll be using than force me to fit filament bulbs knowing i'll change them immediately after getting a new test and potentially alter the alignment while fitting them. Shouldn't happen but it does, especially with minor varaiations in bulbs, hence the need for a beam alignment check after renewing headlamp bulbs even with incandescent filament bulbs.