ireport - field mapping for parent child hierarchy

[awiddowson]

We have an ireport (3.7) running an mdx query through a mondrian connection. Mdx query is 'select {[Measures].[Employee Count]} ON COLUMNS,
  {Descendants(Filter([Organisation Structure.Org Structure].[unit].Members, ([Organisation Structure.Org Structure].[unit].CurrentMember.Properties("MDX Unit Id") = "$P!{UNIT_PATH}")), 1.0)} ON ROWS from [Establishment] where [RecentDay]'

We want the report to show employee count on one axis and the descendent of the parent child hierarchy on the other - at present it is displaying not the descendent on the rows axis but the highest item in the hierarchy.

The field mapping in the report query is set to Rows[Organisation Structure.Org Structure][unit] - I assume I can change this to get the descendent in the hierarchy rather than parent but how???

I've checked the documentation and samples and there are lots of examples where a hierarchy has fixed levels, ie time, but I cannot find any with a parent child hierarchy.