One reason I can think of for the husband to take his wife's last name in the UK is because Fletcher may have made it easier when dealing with other people or the authorities, compared to the foreign Lazarus. Considering common intolerance to strangers/immigrants/Jews, using a less "foreign" name might have helped.
In my family I have the opposite reason for choosing a wife's last name.  I have a cousin in Israel who's last name was originally Cohen. He adopted his wife's last name so he could have a less common name and less confusion when dealing with officials.  His first name is pretty common Israeli name and Cohen is the most common last name for Jews in Israel. Think of being named John Smith and having to explain to the police each time that you are not the John Smith they are looking for.

Dan Efrat
Cherry Hill, NJ, USA (originally from Israel)