Hi
Do you know any more about Zygmunt? Was he married? Did he have siblings or children?
There is a death record on Ancestry for Zygmunt Wisniewski born 9th August 1923, died April 1989, Mansfield, Derbyshire, Nottinghamshire (sic!). Is this your man? Do you have this certificate?
(Ref: Mansfield Reg District, Apr 1989, Vol 8 Page 250)There are two other Zygmunt Wisniewski deaths:
born 4/3/1923, died January 2000, Haywards Heath, Sussex
(Haywards Heath Reg District, Jan 2000, Reg No 30A, District & Subdistrict 7811A, Entry No 194)born 5/5/1923, died June 2003, Chiltern, Buckinghamshire
(Chiltern Reg District, June 2003, Reg No L9A, District & Subdistrict 327/1A, Entry No 193)There are 8 marriage entries in England & Wales for that name between 1947 and 1980 - I won't reproduce them here as some of them or their spouses may still be alive.
If Zygmunt was married in the UK, then his marriage certificate(s) should have details of his father's name and occupation, which may help you with previous generations.
There are also Wisniewski records on the National Archives website:
http://www.nationalarchives.gov.uk/search/search_results.aspx?st=q&queryText=Wisniewski&aqgQueryText=Wisniewski&queryType=ALLNote that the origins of some Wisniewski or variant names are Poland, Russia, Germany.....
Kind regards
Gaie