£330 for one charge is excessive. You should ask for a breakdown of the charges. They have no legal basis to charge you the excess amount as they are merely invoices as opposed to fines. Normally with these private companies, they do have a claim for breach of contract but only to recover monies they have lost and not for excessive amounts. Inform the solicitor you refuse to pay such an excessive amount put them to strict proof of the alleged offence.
If you cannot arrive at a more reasonable figure to settle i.e. whatever the original charge was, then you should look to defend the matter. This may mean they will have to issue court proceedings, this is the only way for them to recover the funds. It is unlikely they will as it isn’t cost effective for them to do so, as cost of court proceedings is more than what they can recover but some companies do issue and if this is the case, then you’ll need to ensure you defend the matter.
Unfortunately it is too late to appeal now through the correct procedures as it has been such a long time, so your options are to pay or defend it. If you defend it, then as stated ask the for proof it was you, ask them for a breakdown, make them justify their claim. If they cannot, I would suggest you defend the matter at court.
Thank you again for visiting JustAnswer, please let me know if you need me to clarify anything or if you have any additional questions. I am happy to help.