I'm asking you to substantiate your claim as regards notifying DVLA.
And back to procedures. What happens when the scenario you posted occurs is that prudent people arrange for mail forwarding. But it's not compulsory.
And yes, the process grinds on to the NoE, the agent's duty, even perhaps a visit, whether by them clamping a car or visit to the house.
At which point owners have the right to follow the procedure numerous posters have set out for you. This is YOUR chance to explain why you did not receive the PCN and if the Traffic Enforcement Centre are convinced then the whole matter is reset, any monies paid are refunded and the owner makes their case to the authority from scratch.
But owners need to engage in the proper manner and not think they can circumvent procedure and vent their spleen against the agent, after all they didn't issue the PCN neither have they anything to do with the PCN enforcement process.
In your case you've neither told us when you vacated address A, or when you notified DVLA or how(other than in vague terms) and without these key facts IMO you limit your chance of success. Of course it's possible that the V5C date on its own might suffice when set against the contravention date, particularly if the PCN was not served until after the V5C date.
But you seem so set on going your own way rather than supplying these simple facts that you risk all the nuisance and inconvenience which a visit from agents can bring.