Hi
Only if nothing is found online or websites and nothing is found by members on this website.
Try posting on this website GENERAL BOARD as people who go to the Sheffield library or live near the archives who go for books and other business who don't do ancestry may do a look up for you.
http://www.sheffieldforum.co.uk/last resort!
South Yorkshire Sheffield Archives is one of the few archives that have the only film/fiche is I know of, as the Sheffield library come under the same authority, meaning they charge the same as the archives for searches charges that are high!!! with no free look ups and same with Rotherham. Most (Not the old West Riding) as now West Yorkshire (Not all) main libraries have PR's on film/fiche and do free 1/2 hour look ups or searches.
If family history societies or LDS/Beta don't have the info for Sheffield marriages in their index then Ancestry.com/co.uk may have them transcribed and either join as a subscribed member or use a free library edition at most libraries world wide.
Last considering you need to find the church they married at to find the church PR entry of the marriage to have a church register entry info being original or transcribed copies (Transcribed maybe indexed) (Sheffield arn't indexed on all marriages in all church Pr's) is what will cost the most in a search and charges as much as £ 30 a hour or more (With or not a find and 1 hour is not much time for blanket searches), it may be cheaper to buy a bulk GRO marriage certificates buy from the Free BMD GRO index numbers or Ancestry.com free BMD GRO. index
Dobfarm