Hi ec
Folllowing a serious senior moment I misread Henry as William and searched for Jane, born in Pancras, daughter of William and Sarah. Hiraeth's discovery may mean that this was an incredibly lucky error. The 1881 census has the following family living at 6 Coopers Buildings, St Pancras (RG11/192 19 p32-33 )
William Boon, Head, marr, 44, Jobbing Labourer, b. Middlesex, Pancras
Sarah Boon, Wife, marr, 36, b. do do
Edward Boon, son, unm, 14, b. Middlesex, Pancras
Frederick do, son, 10, scholar, b. Middlesex, do
Elizabeth do, daur, 9, do, b. do do
Charles do, son, 8, do, b. do do
Jane do, daur, 5, do, b. do do
Alexander do, son, 2, b. do do
James do, Brother, 26, Auctioneers Porter, b. do do
I think that this lot are worth a closer look given that your other thread mentions Frederick Boon as a witness at Jane Bryant's wedding.
All the best
Gobbo