i think you'll find thats not true. else halfords sold me an illegal plate.
new car rules must be different to old car rules.
if in doubt just get a set knocked up by a halfords or local garage.
every time i see a girl with italic glitter letters on a black plate on a pos hatch back i feel for the police.
You'll find the halfords plate, if at all recent, (as in last 5 or more years), will have halfords in the lower middle, but very discrete, also it'll show the BS no. in one corner, and postcode of their head office in the other - I think.
Look a bit harder - it's all there.
Dave