It would now appear as if William married to Violet may well be my John William. JW apparently married Violet Dumphy (as per original posters query) Violet died in childbirth (giving birth to Benjamin) and JW then later "married" Violet's younger sister Minnie. I'm afraid I have no further info on John William but I can confirm that one of the Callows did indeed have a grocers shop and a market garden. I suspect the William mentioned in the 1901 census as living next door is not the correct William (especially since her spouse is almost certainly John William Callow) that's not to say however that those Callows aren't related.

I too would welcome some more info on Jown William (and Violet) I have the 1891 IOM census but obviously both would have been single at that time and therefore I have been unable to determine any more from that census on JWC.