Well House Square is/was in Potter Newton, Leeds, just off Potternewton Lane. The impression I get is that it was somewhere behind no 40 (ish). That number doesn't exist any more. The old Shoulder of Mutton (now Inkwell Arts) is no 31, but the property opposite is 74. I'm guessing therefore that Well House Square was on that side of the road, towards the traffic lights. Probably where those little courts of new houses are.
Isabel Newill is at no 3 in 1901, with the Ethel, Willie, Mabel and Maud plus a visitor, Nellie Harrison. No ME that night. Could Mary Elizabeth be living-in in service anywhere? I've tried a lot of variations and sneaky tricks but I can't find her. What address does William give for the banns?