#2336 Fix weekly test - moving target

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20472 b5f69653-2bf5-0310-8201-b0dafb8e1405
Get around some existing limitations associated with the cell writer hierarchy (cf. #2422 and #2441)

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20473 b5f69653-2bf5-0310-8201-b0dafb8e1405