Coupe Si 98' Knocking sound

I am looking for some urgent help. 

I have noticed a worrying knocking sound coming from the front LHS wheel, I will be removing it tonight to check for any loose or broken parts.

What I would like to know is if there is anything I may be missing that might not be visible via a quick (mildly experienced) look under the front.

The knocking occurs either part way through a corner or when going over sharp bumps which leads me to think it could be a bush, however there is a definate 'metal on metal' sound to the noise and it happened all of a sudden.

Any advice will be greatfully recieved.

Have you ever had a CV joint fail?  That sounds like classic CV joint symptoms.  If that's the problem, it may drive for a while longer like that, or it could totally break at any time and you'd be stranded.