"Battle of the Somme" entered the consciousness of English folk musicians via the Albion Band, both from their album "Battle of the Field" and their setting for the National Theatre production of "Lark Rise". Their slow version (I'd describe it as a slow march rather than a lament) has a certain grandeur, emphasised by Ashley Hutching's bass line, is the basis for what has become the standard English interpretation. When I hear it played by Army bands at the Trooping of the Colour it sounds too brisk and cheerful to me, although that is how it should be played. Of course, if you're used to hearing the correct pipe version then the English version will no doubt sound turgid. However that's what happens to tunes when they travel.

As for the key, that's a mechanical constraint of the instrument that melodeonists are forced into (just as pipers are forced into their own key and scale), although I play it on anglo concertina in C.