Yes, you're right...I know how to set the currencies but when I click "update currencies" I get an error at the top of the page saying:

Warning: The primary exchange rate server (oanda) failed for GBP (GBP) - trying the secondary exchange rate server.
Error: The exchange rate for GBP (GBP) was not updated via xe. Is it a valid currency code?

Any ideas?
Thanks
Pete