Get the currency for cost price from Unleashed (and not assume home currency)

Some users will buy products in a currency different to their home currency, however when importing product cost price from Unleashed this does not provide the currency, just a number, so this is always treated as home currency.

The underlying issue is that the Unleashed API only provides a number, it doesnt tell you what currency this number is in, so we assume home currency.

One potential work around is to Add a cost-price option that gets cost price from the Supplier product price in Unleashed and converts it to home currency for that supplier... but we'll discuss with Unleashed product team to see if there's a better solution.