international pricing

Update advisory: we explain why we are changing the way we track our currency's movements based on trade-weights. Our own TWI-5 is a different measure to the RBNZ's TWI-17. Both are approximations

Update advisory: we explain why we are changing the way we track our currency's movements based on trade-weights. Our own TWI-5 is a different measure to the RBNZ's TWI-17. Both are approximations