stay away from fibreglass, it will do exactly what you have experienced. I put an original series 3 front lip on my Series1, bolts straight up, except you also need to change the brake ducts over to series3 items.
You can look on yahoo for a original lip, takes a while but they do come up every now and then, just make sure its original plastic, not fibreglass.
Or you could get that guy on here from customcarbon to make you one of his full carbonfibre ones, was around 800 i think.... even then, don't think it will be as flexable as an original plastic one.