Technically Marggie is not correct (sorry Marggie).
Of course any bank can charge what it likes OPO but actually the information on the Nationwide web site was widely miss interpreted by everyone but it would seem, me!
If you read their web information carefully you can see and it was always quite clear to me that when Nationwide stated on its web site that there would be no charge for withdrawals for GBP that is what it meant.
There were about 100 topics on this subject where everyone widely speculated and assumed there would be charges and there have continued to be posts with people confidently declaring they were now charging.
They didn't and still don't - for that we are indeed very glad