As I use bank feeds, it would still be useful to be able to flag it as a non-sterling payment, and then it’ll offer a list of open invoices/purchase orders that are within a few pounds of the amount at the current exchange rate for the invoice/purchase currency, and mark invoices/purchases as paid that way - the same as with sterling.
An example workflow that would minimise the database queries:
1: Press TAG on a payment (in or out)
2: If no invoices in sterling found for the exact amount, offer a “Non sterling transaction?” button
3: If Non Sterling pressed:
3a: Query relevant table (invoices or POs) for customers/suppliers where the currency is not sterling AND there is a balance outstanding
3b: For each result - convert sterling amount to invoice/po currency
3c: Return a list of invoices/purchase orders where the invoice amount is within 15% of the converted sterling bank value (to allow for exchange rate fluctuations)
4: On selection of invoice/PO, mark it as paid with the relevant conversion loss/gain registered.