Its pretty hard to issue speeding ticket to a car that doesn't exist and has no owner.
Had there been no job offer or conduct, then of course there would be nothing to answer, but that is not what we have here.
To answer you specific question: An allegation of a motoring offence is all that is necessary to ask the registered keeper to identify the driver, if he fails to do so without good reason, he commits an offence. All that is necessary for an allegation of excess speed, is for an officer to form an opinion of excess speed and for that opinion to corroborated either by a device or another officer. It is for you to engage to defend yourself.
No Comment is only a useful trick, during the case building part of the process. Once you are before the beak, they will conclude [as is the same in the court of public opinion] that a person who does not protest their innocence and put the record straight, is likely to be guilty.