Search the forum for “Willen” and you’ll find similar cases.
Smart would have rejected your appeal even if you had not identified the driver, as would the IAS. They don’t care about technicalities like the requirements of the law.
Since you identified the driver, you can still file a defence if you follow the process, and it’s likely that although the court process will be started, it will eventually be discontinued. Just not one on PoFA 2012 because you have made this irrelevant.
Your choice as to whether you deal with the paperwork and end up paying £0 or pay up now and be done with it.
If you want to know more, search the forum for Smart, IAS and DCB Legal. Plenty of examples here.
Do nothing, and you will get letters from debt collectors which you can ignore, followed by a Letter of Claim, probably from DCB Legal. To which you need to reply, and for which you should get advice here.
Oh yes, you can appeal to the IAS if you want. It will cost Smart something like £23 if you do. The IAS is extremely unlikely to uphold your appeal, it boasts that it upholds 4% of appeals received.