Trader got held up when he said they require a SIC code, a specific reference description for what the haulier is carrying.
Standard industrial classification of economic activities (SIC) codes relate to the business activities, rather than the load being carried.
If just a haulage company carrying cars and parts then the SIC code could be “49410 – Freight transport by road”
If they are the exporter of the car or car parts then there will be different codes for these. See below