I can't speak to the hypothesis that the English were the first to notate pipe music, but I believe your suggestion that the military may have served as the catalyst has merit. (And that, of course, implies that we're referring to the British army of the day.)
Whether 'tis true or not I can't say, but I recall reading in another newsgroup that the first documented record of the existence of an organized pipe band refers to that belonging to a British regiment garrisoned in Montreal, Canada. As I recall, the date was relatively "recent"... 1825 or so.
The military bands defined proficiency as standardization for both playing style and tune settings. That would have implied the need for notation for training to reach that standard and a means to share a common tune list with geographically dispersed musicians.
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