Wellingborough’s population in 1801 was just 3325, owing to an influx of journeyman shoemakers who went there it grew to 4454 by 1821. Subsequent rapid growth was due to the opening of the Blisworth-Peterborough (L.N.W.R.) railway in 1845, by:

"1857 the Midland Railway’s main line passed through the town and the company made it the first great mineral and goods station out of London... Enormous quantities of ironstone began to be mined in and around the town. Blast furnaces were set up for the production of pig iron. Messrs. Butlin’s East End Ironworks provided employment for the rapidly rising population which rocketed from 6382 in 1861 to 18,412 in 1901.

All this brought startling changes to the townscape. Large locomotive sheds were erected, flanked by a mesh of sidings; a hostel or lodging house for engine drivers and firemen was built. Working class terraces in red brick, soon soot-blackened, covered the east side of the town between Mill Rd., and Midland Road..." (Steane, J. The Northamptonshire landscape p.277) (Before moving to Mill Rd., Percy and family initially lived in terraced houses nearer to the railway line.)

The Midland Railway network linked Sheffield - Nottingham - Leicester - Kettering - Wellingborough - Bedford - Hitchin to London, other lines went between Birmingham and London. 

William Orme came South from Nottingham as a Guard. Alfred Omant presumably followed the Railway - first South to Hitchin where he met Mary Tall and then North to Wellingborough - because of the building work. 
Frederick Tall travelled with/after his sister. 
Percy Tall followed his family; he probably initially worked on the railway at Hitchin. 
William Frank Nichols moved there from Kettering, to obtain promotion in the Boot and Shoe Industry.