Free Traffic Legal Advice

Don't worry about being fined for not updating your V5, it is a matter for the DVLA, and nobody who's come on here with your situation has ever been fined.

So advice is to pay the bailiff and then to submit an Out-of-Time Statutory Declaration to the Traffic Enforcement Centre that you didn't receive the PCN. Paying the bailiffs has no influence on whether TEC accept your declaration, but being out-of-time, means TEC will pass it on to Islington for comment, and they will object to it. TEC then reject your submission.

So why was your V5 not updated promptly on changing address ? This is the key piece of information that essentially decides whether the submission is accepted or not. If you just forgot then chances of success are low. Of course, Islington may not object to it, but this is unlikely.
The TEC forms you need are the PE2 and PE3.
https://www.gov.uk/government/collections/traffic-enforcement-centre-forms


There is also a website that deals with this sort of thing : -

www.bailiffadviceonline.co.uk

Whether your PCN was justified or not is irrelevant unless you can get the matter reverted to the PCN stage. If your OOT SD succeeds, you can pay it, or submit reps against it. The bailiff fees and the Charge Certificate are cancelled and you get these back.

@H C Andersen - Tried to write this as a reply initially but believe I messaged you. Putting it here for others.

I have no idea where the figure came from. I think they may be trying to charge me for each extra day it's held (quoting £45) but it feels like they're just making it up. I didn't receive an NOE or any other warning.

The car was parked outside of my house. I initially thought it had been stolen (due to no communication), so I phoned the police and they informed me that the bailiffs had it. There's no backstory. It's just very confusing.

@Incandescent Unfortunately it was just forgetfulness. I moved house several times last year and updated each time, forgetting on the last one.