On the face of it, it appears that a prosecution is now time-barred. Proceedings must begin within six months of the date of the alleged offence.
However, some things don't seem right.
I received a follow up letter to make the same offer again.
What offer?
Before you enter any plea (by whatever method) you need to find out from the contact centre what "review" has taken place and what was the outcome. You need to find out why your SJPN was provided so late, why it was not served by post (as is usual) and why you have not received the accompanying material that should have been served with it (which, as you have not mentioned it, I assume was not served).
It may help if you post up what you have received but I would not enter any plea until you know the answer to all those questions, as well as the one that Southpaw has posed..