Currently automatic product pricing / margins / markup etc is handled via customer and supplier price lists which is very inflexible in its us and a nightmare to manage. My suggestion is to have a pricing calculation structure in the product details themselves so that sales price can be automatically calculated from supplier cost price by margin or markup.
It should also have the option to specify a supplier cost price in the base purchase currency which is automatically calculated to GBP at the exchange rate set for that currency and auto calculates again if the exchange rate changes. The sales price could have the option to change according to exchange rate changes or not.
Additionally it would be useful to have an option of using 2 exchange rates for each currency - one exchange rate to be used for VAT purposes which would match the HMRC monthly VAT rate and another exchange rate that is used for the pricing calculation method mentioned above so as not to interfere with the VAT rate used for invoicing etc but enable accurate calculations for markup/margin purposes.
A particular software that does pricing structure quite well is Quotewerks where you have the option of automatically calculating a sales price based on a number of different factors - see image link.