There is an 1891 birth on freebmd in St Ives for a John Frederick Paddison which fits the 1901 entry you found
The CWGC website has a WW1 death for a John Paddison but not a John F - also the Medal Roll Index only shows John - with the Northamptonshire Regiment
The free 1911 index has a John Fred Paddison aged 19 living in Hunts - have you already checked the entry? Using the instructions below does not show anybody else called Paddison in the same household
Being realistic - without an address it would be virtually impossible to find who he was living with in Sawtry several years later
USING THE FREE 1911 INDEX TO DETERMINE THE CORRECT HOUSEHOLDhttp://www.1911census.co.uk/search/tnaform.aspxOnce you find a possible match - make a note of the county and district in which the person was living
Return to the index and in PERSONAL DETAILS - just put the surname of the family - nothing else
In LOCATION - Select the county and below it - type in the district
In OTHER MEMBERS OF THE HOUSEHOLD - show the full name of the person you have found on the index
Click SEARCH
The 1911 census is strictly pay per view so you will have to buy credits to view the full entry - the above instructions will only help to possibly show others of the same name in the same household