Couple of things rhys...
Your timing was spot on when i checked it, for it to slip it would tend to go completely and smash your valves to bits.
Have you taken the cams out?
Does the code still come up since you've cleaned the sensors?
If your doing the timing, the crank mark might not line up on the first turn of the cam pulley, if it doesnt, rotate the cam pulley again 360 degrees and see where the mark lines up again. Apparently its in sync every two turns.
Havent sorted mine yet, but we done jonzy's as his was out one tooth(cam gear).
Mine needs to come off completely as its out half a tooth(cam gear)(one tooth crank gear) so the auxiliary belt etc.. has to come off and we didnt have enough time to do it.