Thanks rharv, this is getting me closer. I've found my Roland drum kits on the + button menu next to GM2 right above the keyboard. Setting the PAT to the Roland General Midi (which seems to be their version of GM2) seemed to bring these up. The Roland manual actually has only two pages on using it as a synth (not counting the tone chart), and I think I might have a slightly different version from you, as the page numbers don't correspond. But I see where you are looking.

I've still got to disentangle the various patches going through the BiB Melody track (all of the MIDI channels seem to be going through this) but someone else had suggested that I open up the tracks menu, or use RB instead to sort this. I'll have to search around to see where the Tracks menu is on BiB ... but there is some light at the end of the tunnel. Thanks all

Chris