Notice to owner
20.—(1) Where—
(a)a penalty charge notice has been given with respect to a vehicle under regulation 9, and
(b)the period of 28 days specified in the penalty charge notice as the period within which the penalty charge is to be paid has expired without that charge being paid,
the enforcement authority concerned may serve a notice (a “notice to owner”) on the person who appears to it to have been the owner of the vehicle when the alleged contravention occurred.
So, the NTO must be in respect of a specified PCN and a PCN must carry a VRM. Any NTO issued in respect of this PCN number but in respect of a different VRM would a procedural impropriety at best and IMO a guaranteed costs award in the owner's favour should matters progress.
OP, what exactly is this discrepancy?