Actually turns out that this is now moot as I now find (via Roland) that this particular drum box has very odd MIDI functions around program changing - quite bizarre

Instead of moving the DR-3 to the requested Pattern Number ..it moves the Drum Kit assigned to the requested pattern to the current Pattern....WT...??
Makes no sense to me at all!
Should it not say in the manual state DRUM KIT CHANGE instead of PROGRAM CHANGE then?
So now I am looking at the DM1 (iPad) as an alternative to an external device ..and have raiaed another thread to get some answers about how that all works