I think all these notes would look better if you used the Sphinx ~ to reduce the linkword to the main class name
  -- e.g. ```:class:\`~iris.analysis.Aggregator``` makes "An \<Aggregator> instance..." rather than "An \<iris.analysis.Aggregator> instance..."

So, this can be usefully applied to all your "an \<Aggregator> that... of an <\Cube>" notes
( but note :  also need to change "**an** \<iris.cube.Cube>"  to "**a** \<Cube>" everywhere )

@ajdawson put me onto this.
See http://sphinx-doc.org/domains.html#cross-referencing-syntax.