Welcome to the forum,
Chasing power is always going to be very expensive. ITB's and cams are a good way to go if you are set upon more power. Induction kits are supposedly not very effective on this car, Fastcar magazine did a dyno comparison of some induction kits and long story short, found they didn't help things at all. However, the ITG maxogen was not tested, and some people think it does improve power. Obviously forced induction is another option, but I don't think many here would argue if I were to say it's not for the faint hearted.
Likewise, if you want better handling, your options are largely expensive as the car handles very well as standard. Coilovers are a good way to go, I have tried a car on Gaz Golds and that made a hell of a difference, but they are pretty damned expensive. Other options include fitting a rear ARB, but that can increase understeer. The best thing you can do for handling is good tyres IMO, depending on what you are currently running, a set of performance road tyres or semislicks could be very helpful. Also, fitting polybushes can make a big difference to cornering and feel, as well as solid top mounts, and these cost relatively little.
I've never had a problem with K-Tec, although be a bit careful because some parts can be had for less elsewhere. RoadTrackRace parts are good, as are Renault Parts Wolverhampton, but I have no idea whether they will ship to AUS.