ah ha!!!! its the front light level sensor that is connected to the front suspension arm. this has to be disconnectd and reconnected when doing the clutch, it is very easy however to refit it 360 degrees out of plonk which will of course affect the headlight leveliing. it takes about 30 secs to unclip the arm off it , spin it round and clip it back on.
here witht eh plastic arm, under the front right hand wheel arch
the pressed tin bit is a cheap cover instead of having a higher quality finish nut - although the tin bit makes it up to 19mm, i found using a 12 point socket damaged one of mine - u need to use a 6 point socket and make sure its pushed fully onto the nut before tighting up.