Firstly, you say that the Bailiff told your next door neighbour how much you owe??
This is a blatant breach of the regulations re enforcement and the information protection rules, you may wish this to be looked into when all this is sorted. but first thing first.
The initial part of your hearing will be to decide whether the court excepts your story about not knowing about the missed hearing, if they do accept it, the next stage will be the hearing regarding the offence itself. In particular whether you were owner of the car or not .
For the first part, you need to show evidence that you were not at that address when the summons was issued, this you should be able to do with a rates bill or any official dated correspondence etc. Addressed to the applicable premises.(your house at the time)
Personally, I would think they would accept your claim about not receiving the paperwork, but that's just my opinion based on what you said.
If they do they may immediately start the second hearing, or if it involves a lot of evidence, they may ask you to come back and give you another date.
In either case you need to be prepared with your evidence. They will ask how you plead. If I were you I would plead not guilty as, you say you did not drive the vehicle nor where you the owner at that time., but mention your concerns about none delivery of your documents and seek the clerks advice.
On hearing the full facts I doubt the judge will let you plead guilty anyway. Unless you are very insistent.
Your evidence here would be a bill of sale dated or a record of cash flow in bank statements etc.
Good Luck and dont worry it is not as bad as it sounds, no one is going to prison or anything, and if you do get a fine you just ask for time to pay. Worse scenario.
We need to know the car make and exact model, petrol or diesel and if it's an auto stop/restart model. The battery model and maker would help too.
Then we can see if you have been as badly overcharged as you say...........
........ and maybe give you some suggestions.
Don't touch them owe me £500 since January 2019 make excuse after excuse. Seem they always have software problems sending money out. Keep saying they will call back or email nothing been chasing it now for 6 mths the phone staff always have the same banter we will chase it up and get back to you then nothing!