Thank you so much, Artful Codger. The Wexford Carol's textual basis will be this ballad, then. To my ears, The Wexford Carol is an improvement but, as you rightly say, the evidence says the finished product is well outside of The Night Watch dates. We could work up an arrangement of the broadside, but we already have plenty of songs - it's tunes we're looking for (as stated in the original post).
Thanks all, once again. I didn't expect so many responses - and of such quality, too - to what I thought may be an esoteric request. This is Mudcat at its best!