Not strictly in Melbourne as such, but there is also the Mornington Peninsula Astronomical Society (used to be Frankston society). If you are down this way, it may be convenient to you. I am a member of ASV and MPAS and enjoy both of them for various reasons.
I don't know about the others, but the ASV also have renta-dobs (8") I think, for members to use, which would be useful if you're tossing up buying one yourself