Are you sure the GPX data is in GDA94 zone 55? As far as I know GPX is always EPSG:4326 lat/lon degrees so make sure that the GPX data is actually in GDA94 zone 55.
Thats independent from any CRS you have selected in BaseCamp, QGIS or your GPS unit.
If you want to have your coordinates in GDA94 Zone 55, load the layer as EPSG:4326
, and save it with rightclick -> Save As ...
into the CRS you want.