Oh yes, indexed as Goodwin on ancestry - they obviously thought the Dax was a 'Do' from the Goodwins in the house above which, annoyingly, I've found lots of times with them.
But, yet again, Mary Anne is not with the rest of the family. She is NEVER with them and yet on her marriage certificate it says father William Dax, Grocer and the witnesses include Margaretta and Henry Dax - who are later children of the family unit you have found in '41. I suppose, outside chance, it's a different William Dax who is her father, and the witnesses are her cousins, rather than siblings, but that would mean two Dax siblings both called William, which would be very odd.
The family next door is also interesting - headed by Mary Withers, the surname Withers keeps cropping up in connection with the Dax's, Mary Anne is staying with a Withers in '51, and I have it down as a possible maiden name for the Mary Dax shown (but that's a pure guess) and they have a M.A. Dax ........ hang on, IT'S HER !!! M.A.Dax MUST surely be my Mary Ann, the age written could be anything, my Mary Anne would be ~4, this age could be 8 or 6, but it could also be 5. And another of the Goodwins in the same house is a shopkeeper, which ties nicely with Grocer later on. I think the two households are connected !! Also the surname 'Breeze' keeps cropping up as well.
Thank you, thank you, thank you - I think you've not only found her parents, but you've also found HER without realising it !!!!