Footnote separator line too close

[Richard Shann]

I've found that the line dividing the footnote from the music is rather close 
to the footnote text.
I can see I need to override this definition

footnote-separator-markup = \markup \fill-line { \override #'(span-factor . 
1/2) \draw-hline }

but I can't see what to add to provide more space under the line ... any 
suggestions?

Richard Shann