Now if the family I found above are the ones:
1871
RG10/1488 21 3
23 College Street n°7 Court
Thomas George, head, 41, Jobbing Labourer, b. Northampton
Susannah, wife, 33, b. Coventry
Emma, dau, 14, Fitter of Shoes, b. Northampton
Thomas W, son, 13, Costermonger, b. do.
Then after much searching I have a feeling they were called Webb in 1861 (RG9/2178 5 3), which isn't going to make things easier for us

Maybe the best way to find out her maiden name is to order Lily's birth cert after all - or even Susannah's marriage cert to Mr Parsons, which would show her father's name.