Just in case Thomas Cahill turns out to be the right one ...
I think I can see him in 1851, lodging in Worcester St Martin with a Davis family, age 6 born Claines (HO107/2042 473 48)
In 1841, there's one matching Cahill family in Claines:
HO107/1209/5C 24 19
Back Lane
William Cahill, 25, Coach Smith, Ireland
Maria, 25, Ireland
Marcella, 3, Ireland
James, 5 mo, Worcestershire
Maria and Marcella die in 1845 (Thomas is registered in Dec 1844) and by 1851 William is remarried to an Elizabeth Davis.