If its insured and taxed, mot'd in someone else's name and you buy it then so long as you are yourself insured it shouldn't matter in the unlikely event that you get pulled over.
All ANPR will show as its taxed for that day.

So just get insurance and should be ok.

When my 3dr got wrote off it was not taxed, it was in sured and had just half a mile from the crash passed the mot.

Coppers done the checks and said its not taxed so best get it done asap just incase - which i did. Then it was wrote off by the insurance.