Very nice bike Nigel
I think I have the same RE leather panniers in black. Hydrophane really does waterproof leather
I don't have the pannier scorcher silencer, nor that pillion seat. Is it comfortable? To be honest, it looks like a torture device

Wife complains the stock pillion is not wide enough even though it is wider than the Bullet dual seat. I do find the stock solo seat to be very comfortable, I have dropped its rear by removing the springs for brackets, not only to lower it but to make it firmer, no padding wanted. Those rear suspension units are really rather good.
I could not get the panniers to hang nicely on the mudguard frame. I think the various advertisement publicity shots must have used sticky back plastic to hold them looking nice and square. I adapted the "Electra" small pannier frames, they do fit with a bit of bodging but only to the C5 stock pillion frame seat (an extra) which is similar to the Bullet dual seat grab rail but about 1cm further aft.