Volume namespaces - fixes 771

Fixes #771.

Some temporary code is in place so this doesn't break the rest of the system.
This appears to be deliberately testing the inequality of values against the overloaded comparison operators, so the use of `==` against a `False` result looks intentional, likewise for `!=`

:question: though - doesn't characteristic have its own tests for comparisons, are we not just re-testing that already?