Iain: I think that Sellars & Yeatman attribution of the Parliamentarians being “Right but repulsive” and the King’s men “Wrong but romantic,” is misplaced. There was plenty repulsive about the Royalists. “Upper-class twit” was not a 20th-century invention.
However, it is interesting to note that some similar schema has been applied to the American Civil War in the popular imagination. “Sure, slavery was wrong and all that, but… how romantic those Southerners were! Compared to the dull plodding Union cannon-fodder…” At any rate, I don’t know how else to account for the (apparently) perpetual popularity of Gone With the Wind.
In some respects, in fact, the U.S. Civil War was just a replay of the British one. The “tidewater South” that supplied much of the officer corps were descended from the “distressed cavaliers” who fled England after losing to Cromwell and his boys. The New England troops were of Puritan descent… etc.