You must apply for a mandatory set aside under CPR 13.2. The claimant is under an obligation to make sure that if they receive no response to anything that the person they are pursuing still resides at the last known address.
Updating your V5C and drivers licence after you have received the original PCN means nothing. They were only allowed a single bite when they refused your DVLA data at the time. They cannot go back for it again.
All they had to do was a soft credit search and they would have likely found your current address. They didn't. Of course, if you'd remembered to update your address for service with them, this could have been avoided. However, that is not really your fault if they had not yet initiated any proceedings.
It will cost £313 to apply for the set aside but you will ask for those costs to be paid back as the claimant has acted unreasonably because they did not make any effort to find your current address after they did not receive any response to the LoC.
It just means that this is now dragged on for much longer than it would have.
Your very first act must be to phone the CNBC, preferably very first thing in the morning to avoid very long hold times. You must ask for the Particulars of Claim (PoC) to be emailed to you, while you wait on the phone. Also, get confirmation which address they used for service and the date the claim was issued and who, if anyone, represented the claimant.
This is all very important information that is needed for the set aside application and will also firm that if the claim was not served within 4 months of issue, it must be struck out. You need to act promptly.
Once set aside, the CCJ will be totally expunged from the record. It will not affect any credit applications in future.
So, first thing is to get the information I explained above, from the CNBC. Once you have that, show us the PoC and tell us who the claimant is (original images have been deleted) and, I am going to presume that they were represented by DCB Legal, but please confirm.
Once I have that info, I will guide you through the set aside application and process.