Thank you once again. Looks like a little more work required on my part
It worked when I was looking for my grandparents' marriage. As they both came from Hull and ended up living in Manchester, it was the only way to fiind out that they actually married in Newport, Monmouthshire.

I ended up writing down all the reference numbers of men with the same name as my grandfather and did the same for all the women with the same name as my grandmother, who had married between 1901 when my grandfather was 16 until 1908 when their first daughter was born. Eventually I found a match. Not sure why they weren't on FreeBMD but they weren't.
Finding the birth of their first daughter was another problem. In the end I got her death certificate (modern she only died in 1990 so place of birth shown too). She was born in Scotland. When I mentioned it to my mum she said "Oh I knew that I could have told you if you'd asked!"
Lizzie