Land of Hope and Glory is used as England's 'anthem' on occasions such as the Commonwealth Games, when an athlete's success has to be marked specifically in a way to show his/her Englishness as opposed to Scottishness, Welshness or Northern Irishness...not to mention Australianness and so forth!
However - as Pippa says above - the 'land' in the original version referred to the UK and not just to England. It was, after all, a line in the Coronation Ode written by AC Benson to accompany Elgar's Pomp and Circumstance March No 1 music. It was for Edward VII's coronation and he - just like the present queen - was monarch of Great Britain and not just England.
So, it is a �national anthem' only in the sense that 'Flower of Scotland' is a �national anthem'...ie merely an occasional one.