Only send the currency that matches the account. If you send a currency that is different to the account, you could be charged more or it may not arrive.
For example, if we receive a Euro payment into your GBP account, we'll have to convert the Euros using our daily exchange rate and add 2%.
You can only receive Euros into your Euro account. Any other currency (including GBP) will not be processed and will instead be returned to the payee.