Obviously I can only give you a general answer as you haven’t come back.
If you are asking whether they can prosecute you then sadly the answer is yes.
These fixed penalties are an invention of the police. They don’t exist in law. They certainly weren’t provided for by Parliament. The purpose of them is to divert cases from court.
The reality is that, come what may, they didn’t get your licence so couldn’t add points. I realise that wasn’t your fault but that doesn’t change the fact. They have turned to a summons because they only have six months to lay an information or they will be time barred.
The question is whether you have a defence to the substantive charge. If you were going to accept the FPN then I suppose not.
If you plead guilty though and mitigate on the basis that you tried to accept but failed for whatever reason then they may give you a fine of £85 and the surcharge of £15 plus 3 points. I have seen magistrates do that many times. It can’t be guaranteed though.
There is one option that you could try; I think you were thinking of it anyway. Write to them and declare your ignorance and make clear it was all your fault and ask them to let you accept the FPN. They can do it when it suits them.
Can I clarify anything for you?
Hopefully, I have answered your query in a way that is simple and easy to understand. If anything remains unclear, I will be more than happy to clarify it for you. In the meantime, thank you once again for using our services.