As regards technical defences, the devil is often in the detail. In your case, it appears that the devil has taken the details, and re-arranged the words to say something else (IOW your account clearly lacks accuracy).
However, to prosecute you, court proceedings would need to have been instigated within 6 months of the alleged offence. Whilst the papers which are issued to instigate court proceedings do not strictly need to be served within the 6 months, they should be served without undue delay (within a few weeks). Unless everything was being sent to a previous/wrong address (which is inconsistent with you receiving the NIP and COFP), the fixed penalty is being returned for some other reason.
As regards the forum suggesting that you should have sent off your licence, please point me in the direction of the offending post, and I will deal with the bullsh*tting tw*t responsible.
