Hi Steve (+ others)
We have looked in many Parish Registers in Hull & Sculcoates for this marriage and have come up with nothing. There is a chance they were married elsewhere (Whitby for example) but nothing has shown up to date.
I know they were in Hull from March 1876 onwards.
On her children's birth certs they show her surname as formerly: Moss, Richards, Allison (this was her birth name - Ann Elizabeth Allison).
A clue might be found if anyone can find out what happened to Oliver Richards - he seems to have vanished completely after 1871 census.
She also married again (after the death of James Bibby in 1883) - to James Beckett in 1893 and that certificate names her as Bibby and says she is a widow...could be a fib of course....