Yes the plate should have its own (white) lighting.
It can be incorporated into the brake light, but it must be properly done and not just the red of the back light illuminating it.
A lot of manufacturers do this, but theres a little blank in the red colouring of the rear light so that the white light of the bulb shines on the plate.
As above it **is ** a legal requirement. But it is not an MOT requirement (for a bike only) at all. So either you can have a number plate light that is broken or not have one at all and it will pass a MOT. The only reason it should fail an MOT is if the white light of the number plate light is visible from the rear.
Whats stopping you taking the rear light off and rubbing down the inside underneath so taking the red away thus allowing the white light to shine down on the plate. If any of that makes sence:D
£60 non endorceable (so no points) IF in the very unlikely (IMO) event that a policeman wanted to do you for this. You would of had to seriously pi$$ them off & they couldn’t do you for anything else.
I have just bought from just Bandits (£10) two Nuts and bolts with white LEDs which are really simple to swap with existing number plate bolts. All you do is plug in the number plate light wire into these.
And the look wicked.
Also I think you need a red reflector as well as a light.
My rear plate is lit by bright blue LEDs (not my choice, just never got round to changing them) and I have ridden all through the winter to and from work in Victoria. Must have had literally dozens of police see it and none have bothered me about it. I have changed the plate to a standard size and font, though.