For what it's worth: the pipe tune dates from quite a while after the battle (I don't think there were any pipers at Waterloo anyway), but it's a version of a much older tune. It derives from Tannahill's song "My Braw Highland Laddie", which in turn used a Gaelic song air, "Mor nighean a Ghiberlain" (Marion the beggarman's daughter) which was first put down on paper in the 1740s. There is a fancy arrangment of it in one of Oswald's collections.

"My Braw Highland Laddie" is a standard ceilidh band dance tune, you should find chords for it easily.