A few years ago I wrote to the train operator at the time requesting the Victoria train run later than 7 and more trains on a Sunday (the service used to be pretty poor on a Sunday). I received a standard response, though was pleasantly suprised when both points were addressed in the next timetable.

I think if people do communicate en masse there is a good chance of things being taken on board. If we want to be smart about it, we should set up a template letter and who to write to so things are made as easy as possible.