Hi!
I had a bit of a look. There is no one else on any of the censuses called Portallion, or even close to it. I didn't find Leon until the 1891 census - was he in France until then?
1891 RG12/219/16/26
8 Red Lion St, St Andew & St George, Holborn, LondonWilliam Allen, head, mar, 41, cab driver, b. Tiverton, Devon
Emily Allen, wife, mar, 34, b. Bow St, London
Emma Houghton, head, wid, 70, dressmaker, b. Clerkenwell, London
Leon Portallion, son, s, 26, Corn dealer's assistant, b. France
James Cox, head, mar, 55, hospital porter, b. Abbotsbury, Dorset
Luisa Cox, wife, mar, 55, dressmaker, b. Portsea, Hants
FreeBMD: Leon Portallion married Elizabeth Winnitt Meagher Jun qtr 1891, St Giles, Vol 1b/884
1901 RG13/412/5/2
164 Newington Buttr? Lambeth, LondonLeon Portallion, head, 36, Corn dealer's shopman, worker, b. France (British subject)
Elizabeth Portallion, wife, 35, Norwood, London
Edward Portallion, son, 8, b. Holborn, London
Frederick Portallion, son, 5, b. Battersea, London
(next page)Margaret Portallion, dau, 1, b. Lambeth, London
FreeBMD:Edward Charles L Portallion born Mar qtr 1893, Holborn, Vol 1b/673
Frederick T J Portallion born Mar qtr 1896, Wandsworth, Vol 1d/618
Margaret M M Portallion born Sep qtr 1899, Lambeth, Vol 1d/377
Leo Philip Portallion born Jun qtr 1903, Lambeth, Vol 1d/394
... and of course there may be more children, but you'll have look through Ancestry's BMD images. Shouldn't be too difficult to identify because it is a very uncommon surname.
Cheers
Koromo
