Dublinpilot
I asked a similar question
here recently which elucidated the reponse that there is no such thing as a 'fuel emergency' in the UK, just Pan or Mayday.
As to the paperwork, MOR's were mentioned but no-one commented from a specifically GA point of view, so it would be interesting to know what happens in reality.
I am sure that many (most?) GA pilots would be reluctant to call Mayday out of fear of possible consequences, so perhaps a better knowledge of what follows such a call would help pilots make the decision earlier.