To achieve your desired profit margin, take the total plated cost and multiply by the factor shown. The results show the selling price including VAT @17.5%.
E.g. if you want to make 65% profit margin on a plated cost of £1.98, it would be a sell price of £1.98 x 336% = £6.65
For an instant calculation, use this Ready Reckoner (includes VAT @17.5%).