Tom, did you clean the disk and pads with meths before fitting?, being a real brake friction material, it will get irrevocably contaminated from oils used to stop the disk rusting in the packs, in other words, the pads will never grip if they get the wrong oils on them and it soaks in.

Actually I worry a little about diff silicone fluid getting on the disk and pads myself, cause I know that will root friction material as well...