This fascinates me. Good to know that Deb is sending for that marriage certificate. Bellis is such a rare name that the odds against two people of that name marrying must be huge - unless the parties concerned knew each other as cousins, for instance.
But brief investigation finds this is unlikely. Leigh Robert Bellis I was born in Prescot district and his father Robert L Bellis was almost certainly Robert Leigh born 1889 Chester (if not Robert Llewelyn b 1885 Wrexham) . However the lady he seems to have married was born Dewsbury district and her father Cornelius was born Islington, (his father a Henry Bellis, there are plenty of those) and she also married in the London area. I also fail to see why a woman who had married 1965 would marry again in 1975 without at least giving her married name as an alternative.
My guess is that the lady in the 1975 marriage is giving her surname as Bellis because she has been using that name for many years as a common law wife (I have a couple of examples of this in my tree). If the marriage certificate shows that both parties were of the same address that's a big clue, but hopefully it should also show who her father was, which would be the most useful data.
Chris