RANKX excluding soem items problems

[masplin]

I have only ever used RANKX in a calculated column, but now tryin to use it directly as a measure. I have a pivot table with [Deot Name] as row and values is a measure "Data Score". I want to rank the Depots, but excluding Headoffice. I can easily rank every thing using

RANKX(CALCULATETABLE(ALL(Invoices[Depot Name])),[Data Scores],,0,skip)

However I can't work out how to exclude HO from the rankx calculation. My logic says that this should work, but I get the same answer. My logic is the inner CALCULATETABLE creates a table of all depots, then the outer one should exclude "Bristol" from the table before the RANKX is performed.

=RANKX(CALCULATETABLE(
                                                CALCULATETABLE(ALL(Invoices[Depot Name]),
                                                Filter(Invoices, Invoices[Depot Name]<>"Bristol")
                                                                              )
                                              ),
[Data Scores],,0,skip)

Any clues why it doesn't work appreciated as seems the filter expression just swamped by the ALL.

Mike