Replace your body panels with genuine items, well worth it in the long run, and not really that expensive,
Non O/E are poor quality steel, poor fit, and will definatly not stand the test of time, as regards corrosion.
I consider pattern panels as a last resort, to keep an older car, that has been accident damaged, "on the road"
If, however, your shell needs new rear wheelarches, pattern panels will only be as good as the person that fits them
O/E wings are £80ish good rust free 2nd hand panels, can be picked up for around £30-50 each, or look out in the parts section of this forum for great deals
Tom