if they[Bach,OCarolan] were using a well tempered scale,and not a mean scale,Why should we use a mean tone scale now.

For Bach, "well tempered" meant some variant of meantone (he tried a lot of them). For Carolan we have no idea except that he saw himself as working within the Continental European idiom we now call baroque, and if he expected people used to playing Geminiani to suddenly use a special tuning of his own, he would have had to say so.

How on earth would you keep a harp in ET using the resources Carolan had?

finally, before you dismiss wikipedia as bollocks

I was dismissing that particular article as bollocks. The Wikipedia article on exterior algebra is great. The one on lindane is shit too.

please provide a substantial list of tunes that are in the traditional repertoire,and PROVE when they were composed and that they were intended to be played in mean tone.

I already did - a few hundred mid-19th-century Scottish flute tunes. Buy my CD-ROM and you get a few of them transcribed, along with bibliographic details and the fingering chart for six-hole flute which cannot possibly permit ET playing.

Meantone is not the only non-equal temperament used in traditional music from the British Isles. The Highland pipes are wildly different, with a sharp D, a neutral C, a sharp upper G and a just lower one. You sometimes hear Highland fiddlers trying to fake some of that. And there are a few Shetland tunes that use a neutral seventh (this probably comes from Scandinavia) - you get the same thing in Cape Breton fiddle music sometimes, see the Greenberg & Dunlay book. Neutral thirds and sevenths are a doddle on a recorder if you're playing in the usual keys.

ancient Pythagorean tuning

Pythagorean tuning is more mediaeval than ancient. The ancients thought about it but seem not to have used it extensively in practice. In the Middle Ages it was the only way to go. It makes particular sense when playing mediaeval-style music on the harp.