Birth - I have the baptism record not the birth certificate (my mistake.) Shows William Loveday baptised Feb 1845/46? Father James Thomas and Louisa. Living on Enoch Court which I believe is roughly around Tower Hamlets/Whitechapel. (Not on certificate but father was a surveyor, mother's maiden name Pemberton. I don't know their dates.) I presumed this was the Jan-Mar 1946 BMD in Lambeth but might be wrong.
Gemma, it's this one.

LOVEDAY, WILLIAM, MMN PEMBERTON
GRO Reference: 1844 D Quarter in STEPNEY Volume 02 Page 476

His age is about right to tally with the 1881 census, and Stepney is very near Bethnal Green.

All this isn't get us any nearer to finding why William added Leon Gambetta as middle names after his second marriage. It perhaps is just a case of him admiring the French statesman. Odd that he's entered as born in France in 1911.

Still looking for a first marriage and the 1871 census.