I quickly threw a spreadsheet together that gives an overview of the damage (column H), which is mainly where I suspected plus Ticino. 750 municipalities in total.
See http://he.poole.ch/GWR-redaction.ods
See http://qa.poole.ch/ for roads completely without a name, some of the now "missing" names are likely to be false positives (OSM has a surveyed name that doesn't agree with what is in the GWR), how best to handle these, see: http://wiki.openstreetmap.org/wiki/OSM_-_GWR_Street_and_Place_Names_Comparis...
Simon