I was of the understanding that Flower of Scotland's designation was an informal understanding that it was the Scottish sporting anthem, whilst on other occasions they used 'Scotland the Brave', and there wasn't a formal designation of a national anthem?
Either way, I think the formal adoption of an anthem for England ('Land of Hope and Glory', I think, has been suggested a couple of times) would serve to increase the evidence that England and English people don't necessarily think of England and Britain being functionally the same thing.
O.