The value for import clearance must be at least the amount the goods cost at the border. What this means is that the cost of the goods, the freight, export clearance at origin, marine insurance, and any other charges incurred before arrival must be included in the value for customs.
When your INCOTERM is Ex-Works or F-level (FCA/FAS/FOB), the freight cost is not included in the value of the invoice, so this must be added when submitting your import declaration. Similarly, insurance must be added for these INCOTERMS, as well as C&F as it is not included in the invoice value.
Universal Customs Clearance provides import clearance for all major UK ports. If you are unsure whether you need to add more values to your clearance, contact us for assistance.