Hi -- Was there ever a court judgement issued against you ordering that you pay this fine or any costs added. ?
Do not be bullied --- If not these so called bailiffs are not official.... they are merely employees of Newlyns debt collection agency, they have no legal powers of entry whatsoever. If they visit you do not let them in to your house or offer to pay them anything at all, then tell them you want them to leave your property otherwise the Police will be called.
You need help to challenge this as there are only certain "reasonable" costs that can legally be added to your parking fine, a disproportionate punitive charge of £410 added onto a £30 fine is unlawful, totally unreasonable and excessive no matter how many times they allege to have visited you.
I suggest you take any associated paperwork ASAP to your local CAB for their free assistance in this matter, they could write to Newlyns to set them straight and complain on your behalf to the OFT.... who have the powers to take the approriate action against them for their blatant breach of the fair debt collection guidance regulations.
http://www.citizensadvice.org.uk/cabdir.ihtml