The free 1911 index has a John & Ellen Costigan living in Hampshire who seem to be the same couple as the ones listed in the 1901 in an earlier reply. I personally don't think this couple are the parents of Winifred & Michael given their ages etc
Full details cannot be posted because of copyright restrictions but you can find their household etc as follows
USING THE FREE 1911 INDEX TO DETERMINE THE CORRECT HOUSEHOLD
http://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 surname in the same household
You can check birthplaces for free using GRU
http://www.GenesReunited.co.uk/search.page/index/census_1911Where was Ellen's maiden name obtained as there is no marriage and no childrens births?
Does your friend have a copy of Winifred's or Michael's marriage cert confirming their fathers name and occupation?