Interesting that you should pick on the earlier correspondence about the origin of our name. I can't quite recall when it began: maybe about six months ago; what attracted your attention to it now?
I still favour the 'occupational' origin (i.e. coal mining, as suggested in the geography text book of yesteryear by Jasper H Stembridge, most probably now out of print), but I suppose that there could be several different origins, as suggested by other correspondents of six months ago (Dutch, van Cleef; Cliff as in location; etc). One correspondent, commenting rather severely on my advocacy of the occupational origin, did point out that surnames generally came into being in the 13th century, whereas coal mining as an occupation probably only dates from the 17th century.
As to pronunciation: stick to Collins ... I have yet to get anyone to 'hear' the 't' at the end of our name: there must be a good deal of high frequency deafness about!