Excel’s reply is a standard stalling tactic. They are avoiding dealing with the substance of the appeal and are trying to manoeuvre you, the Keeper, into naming the driver. You must not do that.
Excel are perfectly capable of processing a Keeper appeal and they know it. The Notice to Keeper was issued under Schedule 4 of the Protection of Freedoms Act 2012 and includes the statutory wording enabling them to hold the Keeper liable. They cannot now refuse to consider the appeal unless the Keeper identifies the driver. Nothing in PoFA or contract law requires the Keeper to supply a driver’s name and address. Their letter is just an attempt to flush out the driver to make enforcement easier.
You should simply reply once, briefly, and tell Excel that the appeal has already been submitted, that no driver identification will be provided, and that they must make a decision on the appeal. After that, you should ignore any further phishing expeditions. The next meaningful document should be either a rejection with IAS details or cancellation.
A suitable response would be along these lines:
I am the Registered Keeper and have already submitted my appeal. I will not be identifying the driver. You must now consider the appeal as required by Schedule 4 of the Protection of Freedoms Act 2012 and issue either a cancellation or a formal rejection with details of the independent appeals process. Any further demands for driver information are unreasonable and will not be responded to.
Once that is sent, Excel will reject it, because they always do. The rejection will contain IAS details. The IAS rarely upholds consumer appeals, so the next step will be deciding whether to submit an IAS appeal for the record or simply prepare for the long game, bearing in mind that your strongest point is that Excel’s own payment system failed and caused the alleged breach. All the evidence you already have will carry significant weight if this ever reached court, which is not very likely.
Save everything from the banking app and any screenshots from the parking app. These will matter later.