Hi Kev,
I fitted spax coilovers allround have rear anti-rollbar. front is k11 hubs and brakes haven't fitted front anti-rollbar but feel it needs it. As for the weight issue well there has been plently of small hatches with big engines that handle 205 gti, 20ltr clio etc Its just a matter of set up. I really feel the car will need an LSD. But need to get it on a track to start playing with it.
A front anti roll will transform your car and takes a couple of hours to mod one on. But i still think a small light engine will be nicer to drive on the limit.