I too thought "trite", but a little perusal finds art and craft intertwined in a very pretty, if insubstantial piece.
Surely it's quite danceable, and gracefully, at the speed the (terriers) clip shows. It does sound nice played slowly, maybe on a laid back sunny afternoon, but the clip with the dancing is the more usually played hornpipe speed, the written crotchets in 3/4 normally being written as minims in 3/2. (and around the speed of the other hornpipe in your last clip, Suibhne, at 4m35)
Key of course doesn't matter unless you have a fixed-tuned instrument in other than equal temperament. But I don't know which temperament(s) Purcell would have used. Any idea anyone? And on this subject, did string players use these temperaments strictly, based on the (whatever pitch they used) A, or did they use mode 1 of the temperament but based on the key-note; or what? Maybe old threads on this,will have to search.
Suibhne, I love your Idea about the common state of music. I believe that "folk" music (undefined, no rows please) is the musical "mainstream" (even though it may be in an underground watercourse), and that all other musics are offshoots.