O.K. PEARCE, Reginald Portbury ( NOT Potbury ) does look like the likeliest candidate.

He was actually born 1891, 28th may 1891 but census dates are often approximations.

He survived WW1 and was an assistant baker in the British Merchant Navy in 1920.

Family address was 42, Aston Street, Cowley St John, Oxford, which is in the Headington/Cowley St John/St Clement/Cowley areas of Oxford.

Father = Samuel born Upton Court Berkshire 1853
Mother = Catherine/Kate born Weymouth Devon 1858/1859

Father was a commercial traveller for a brewery.

Siblings all born in Oxford

Evelyn 1884
Herbert C. 1887 a cabinet maker
Harold S. 1889 a corresponding clerk in a printing works
Dorothy K. 1894

Flotilla of boats crossing the English channel ?, perhaps a part of the raids on Ostend/Dieppe/Zeebrugge. ?

Does any of this ring a bell with his niece.?

Perhaps she may recognise the attached picture. ?

I can't find any records for him after 1920.

Left click the attachment to enlarge it, then right click it to download and save it.