Cheers folks.
Garfly - yup, Riddells wins wrt distance to a train, though to your point, I don't know a lot of these strips, so haven't really assessed suitability (wet weather ops, can leave the plane tied down for a couple of days, etc). YMBT is a wonderful place to live. Driving the Hume to Melbourne gets old fast, though - hence figuring out the flying options.
Ross, Tyabb does sound good. My initial reaction was that it's a ways out of Melbourne, but then again, the other options I've tabled are no closer, really.