Hi Jane

This is the census which mentions Santon:

1861 Cheshire, Birkenhead, district 22, page 23

William Killey head age 43 gardener born IOM Kirk Santon

Mary Killey wife age 42

Zaccheus Roberts Killey son age 21 (can't read) general clerk

Christiana Killey dau age 13

William Killey son age 9

Anna Killey dau age 6

John Killey son age 4

Thomas Henry Killey son age 1

all b Cheshire except Wm sr.

I've used all my searching tricks to try and find William in 1841 in England, without success, but that doesn't mean that he isn't there. As you say, he might be over on the IOM. The trouble is, even if you were lucky and managed to find him, would you necessarily recognise him if his occupation of gardener wasn't stated ?

I see from his death entry that he was born "about 1815", so his age at death and age at marriage both almost match the 1814 baptism in Santon to John Killey and Mary Callow.

I can't find him in 1871 either.