I had a walk around Lilydale a few weeks ago. It is a big lake with two large islands, and is pretty deep up near the outflow. It was one of, if not the first man made dam to supply Melbourne with water, so it has a lot of history. There are carp in it, but I'm not sure what sizes they go to, though due to its maturity one would presume they are big.
The biggest problem there is the foot traffic, there seems to be a gazillion dog walkers and joggers doing laps around it. Consequently, it is highly unlikely you will left alone in peace to fish it, particularly if you are carp fishing. There were only two swims were you might get left alone on short sessions, if you don't draw attention to yourself by putting up a bivvy or umbrella. One of them is very shallow, and the other, the better of the two, currently has a boardwalk/jetty being constructed next it - which is why I left the rods in the car! It's a pity because I think the lake has a great deal of potential, but a lot of contact with the public is inevitable should you decide to fish it
If you are brave enough to get your rods out of the car, I'd love to hear how you go with it???