Since lowering the car, the wishbones are pointing up slightly. This results in having positive camber when the suspension has to "work". The outside of the front tyres wears far quicker than the middle or inner side.

I heard that the wishbone balljoints of a 306 are longer than the ZX one's(it would push the wheel more out) and by fitting them you'll get more negative camber. Anyone tried this route and if so will it be enough to counter the negative effect on the camber by lowering the car?

It isn't lowered alot, just H&R springs to give it a +/- 25mm drop...