Thanks everyone for your input.
After researching all the tyres mentioned, and in the absence of obtaining any information pointing overwhelmingly in favour of one particular brand over another, I settled on the Michelin Pilot Road 4 Trail (what a mouthful!) and had a set fitted today by the guys at Two Wheel Tyres at Blacksoil, just near the Fernvale turnoff from the Toowoomba road.
To run them in I took a short ride up to Esk and grabbed lunch at Enigmas cafe, site of many a hearty breakfast during the Esk gathering. Coming back past Wivenhoe Dam I resisted the urge to peel off and go home via Mt Glorious. The combination of those lovely curves and brand new tyres still coated with release agent could have been my undoing. By the time I got home I'd done 150 klms including some zigzagging so that's enough of a break in period I reckon.
Interestingly, while the rear wheel was off I noticed the chain seemed to be crimping a bit. The tyre man said he was going to mention to me that he felt it was nipping up in a few places too. Strange, it's only done 18K fairly gentle all bitumen klms, it's checked for tension every oil change every 5K klms, it gets a regular supply of oil from the Scottoiler, and the sprockets which were replaced at the same time as the chain show only marginal wear.
I'm not happy with the chain now so I'll replace it but I can't see the need to replace the sprockets, apart from the fact that it's accepted practice to do both at the same time. Before KIWI jumps in and tells me not to be a Scrooge, yes, I will do both, but now comes more research on what chain to buy. This current chain I'm running now was/is an OEM Suzuki one in the recommended size. Any thoughts on chains -- size, brand, expected life?