Free Traffic Legal Advice

Are you the registered keeper?
If so, is the address on the V5C correct and current?

Ah. Checked V5 and I hadn't updated the address.

Yes failure to provide details as well as the speeding charge

The speeding charge cannot succeed as the police have no evidence to show who was driving (and you were not anyway). That comes from your response to the "request for driver's details" which you didn't respond to because you didn't receive it. That charge will therefore be discontinued following your not guilty plea.

Pleading guilty to the "Fail to Provide" charge will see you face a hefty fine (a week's net income), a surcharge of 40% of the fine and costs of around £90. But the biggest impact of all will be your increased insurance premiums. You will have an endorsement code (MS90) which gives insurers a fit of the vapours and you can expect increased premiums for up to five years, with a doubling in the first year being not unheard of.

But I don't see that you have any practical alternative.

As an update, I responded online, admitting guilt to the failure to name the driver. I noted that I'd failed to update the V5 after moving and post redirection had run out.
This morning I've received a notice of the court case result, stating both offence orders have been withdrawn.

Am I correct in thinking there will be no further action, or does this mean it won't go to court but they will charge separately?

On the phone to the court helpline but 60 minute wait!