December 2016: I have just received a Gates "Improved" cam belt kit from UK which includes steel idler pulleys in place of the original (genuine) plastic pulleys. The pulleys look nicely machined, and my first comparison with previously removed original parts from my 2003 Scenic with F4R 2.0 litre engine, is that it is the correct kit for my engine. The reason I say this is that I could only find the Gates "Improved" kit listed for Renault Sport engines, and the nearest model I could find would be the Clio Sport 2 - there are several kits for the F4R engine. One difference I was aware of, and confirmed with the supplier prior to purchase, was that it had a 128 tooth cam belt. There are also 127 tooth belts I think in some engines.
The belt in the Gates kit is a "Power Grip HTD" - which is same brand and type as OE in my engine.
Note, the kit contains a new tensioner pulley, same manufacturer as OE, and retaining the plastic running surface on the pulley, so only 2 of the 3 pulleys are steel. In my case, the pulley which I found was cracked at the first belt replacement, was one of the idler pulleys, and I am not sure if anyone has experienced a cracked tensioner pulley - they are quite different in design. I would have liked to see them all in steel.
It seems quite difficult to pin down the correct "Improved" kit for regular Megane, but the Megane Sport and Clio Sport engines are listed OK.
The supplier I got mine from was Engine Dynamics Engine Dynamics but there are also listings on the Gates (UK) site. I couldn't get anywhere with the Gates (Aust) catalogue.
I also note that Gates have a full racing belt/pulley kit (has a blue coloured belt which is stronger, but I couldn't find info on longevity, which is all I am interested in).
Anyway, I am giving it a go, it does appear to be better than the genuine kit, and cost 105GBP plus 31GBP shipping (just under 2 weeks delivery to Perth), it's good value.
Couple of photos of the new kit, plus pic of OE cracked pulley for comparison.