Just as an aside, my refined list is now looking like this (I've replaced the Street Triple with the Twin Bonneville, although obviously I could test both; however, the Twin does seem far more suitable and the seat is a lot lower):
Larger engines:
Ducati Scrambler Icon
Triumph Street Twin
Yamaha MT-07
Smaller engines:
Honda CMX500 Rebel (a nice low seat due to the semi-bobber styling)
Honda CB500X (a genuine all-purpose bike)
The StreetTwin is the look that's doing it for me at the moment, though - takes me back to the days when my mates were all on Bonnies and Tigers!