Yes, I'm a big fan of Brisbane Motorcycles at Windsor.
As for the diagnostics- I'm not sure what "sealed unit" means, but there is a multi-pin plug under the rear right of the pillion seat (and it's a mongrel to locate, being bound up in the harness) which is the diagnostics plug. I use it for my Gear Indicator Display.
I get my tyres from Simon at Northside Motorcycle Workshop. He's cheaper than Brisbane M/C. I haven't had any mechanical work done by him. He's a one-man show even though he has two bike ramps. A very likeable fellow whose wife runs the adjoining accessories shop and who has also been helpful to me.
So I'd say, on the basis of the experiences here, Des Roberts is handy and cheaper and fine if you get the boss on the spanner, but if you're prepared to ride nearly all the way into the city, Brisbane M/C is to be preferred.