OK, so I have replaced the compressor mounts with new and dished the washers which were flat. They are orientated correctly, like so... >|<
The vibration is inaudible outside the vehicle and is quieter inside but still annoyingly audible. It isn't noticeable when on the move.
Any ideas on how to improve things further? Are there improved mounts available? The pump is 3-4 years old, would a rebuild be likely needed/useful? It isn't an OEM pump I don't think.