I'm afraid I am dreadfully confused here.
First, the marriage posted by The Yokel is not correct. The William here married the other female named Jane Doughty and they appear in later census.
I'm confused because I can find only one William bc.1834 after 1851.There were 2 baptisms at Upwell:
William Poole bp.30/7/1834 son of Leonard and Ann
William West Poole bp.28/6/1835, son West and Mary Ann.
The one who married Jane Doughty is shown bc.1834 Upwell and married as plain William. This is the only William Poole+variants born Upwell ca.1834 that I can find on the census after 1851. Don't know if the William who married Jane is son of Leonard, or West.
I've found who I'm assuming is your great grandfather:
William West Poole b.20/6/1865, bp.16/7/1865 St. Stephen, Hammersmith, son of William (labourer) and Elizabeth.
I note that he joined the army in 1884 (as Pool) with address in Hammersmith and his next of kin given as mother, Elizabeth Ann Pool, of West Church, Cambridge.
There certainly doesn't seem to be a marriage between William Pool/e and an Elizabeth Breeze so they may well never married.
Have now found the family in 1871 but William is shown as aged 30 i.e. bc.1841 - Elizabeth's age is 29 which ties in with a birth date ca.1842 which shows on a later census.
Where/when did William die? Do you have the family in 1881 census?
Quite a difference between circa birthdates 1834 and 1841!
Annette