Thanks everyone for your invaluable input. I've been in hospital and I was delighted to find all the activity that has gone on in the meantime.
It plainly states Gladman on the marriage cert but if Leander had 'an accent' then her pronunciation of her late father's surname may have confused the registrar. Everything else seems pretty conclusive, doesn't it? I have found a Baptism record for her younger brother William Gladwin (2 Mar 1884 at Streatham St Leonard) but it doesn't look like her parents bothered to register her.
My grandmother was Helen Harriet Thorpe so probably named after Leander's mother. I have a surviving uncle, grandson of Leander, who will be very excited by all this. He was only 7 when she died and can't remember much - except she was 'scary'! As to her age, will we ever really know.
Sandra D