Rick, if you weren't "under" the impression that morris dances derived from ancient polytheism, then obviously my exhortation to "get over it" didn't apply to you!
The nucleus of the Christain calendar is the postexilic Jewish calendar. This might be said to be "pagan" in its origins since the Judeans got it from the Babylonians, but the Jews, and subsequently the Christians, incorporated this lunar almanac into their worship. There is evidence of some debate in both cases, but it was generally accepted. Simply telling time by the phases of the moon is not, it was decided, rendering implicit worship to "the host of heaven". Rather, the "times and seasons" were made by the Maker for mankind. The same goes for incorporating the agricultural year into the liturgical year: one can give thanks for the harvest to Ceres, or to El-Elyon. The basic facts of the harvest are the same either way. There is nothing inherently "pagan" about thanksgiving.
In any case, the origins of the calendar have little to do with the question of whether or not the sacrifice of the suovetaurilia to Mars has been made every year without exception since the founding of Rome. It is this sort of continuity which I understood the Gardnerian Wicca to have been making for itself at one time, though I think many Gardnerians have gotten over it.
One of the best explanations of "pagan" I have seen is that it meant to imply "local", the worship of the gods-of-the-place rather than the universal God proclaimed by Christianity.
The use of the uillean pipes in Braveheart was, so I understand, a purely pragmatic decision. The uillean pipes were developed, through the 1800s, into a fully chromatic instrument, and so they are built to concert pitch and can play in any key as part of a larger orchestra.