Transferwise operates a very similar model for currency exchange: you send them Dollars to convert to Euros and they match you to people who need the opposite.

Transferwise operates a very similar model for currency exchange: you send them Dollars to convert to Euros and they match you to people who need the opposite. I guess their model is a bit different in that the exchange only happens once a second party is found, but I think a peer to peer system makes even more sense when converting between currencies, as there is literally no way to turn actual Pound Sterling into Euros, so physical transfer is out of the question.