Ah gee Steve, that looks really nice!
I would imagine that Perth will only be a modest light dome on the southwestern horizon? Magic!
I would love my wife to agree to something like this, although 100km might be a bit too far even for me to travel each day but Perth is pretty big so 100k's is about what would be good for astronomy..?...and yep that's all that really counts, the astronomy!!!

Perhaps have it as a comfortably positioned dark sky outpost for weekends would be good too?
What sort of observatory are you planning?...go on, make me more depressed
Mike