It is not about pay , it is about passenger safety, the health of those working at night, and the right to choose night shifts than it being forced on them.
Tube Strike Is Entirely Justified
http://www.huffingtonpost.co.uk/seb-michnowicz/tube-strike-is-entirely-justified_b_7751262.html?utm_hp_ref=uk&ncid=tweetlnkushpmg00000067