I have a knocking that comes and goes from somewhere in the front right when going over bumps in the road. Some times it is really obvious but then another time it is silent. I get the impression that it knocks more when Ive been driving over 10miles but its not all the time.

I thought it was the ARB bush as it sounded similar to the noise I had before Christmas when the garage greased it up and it went away. I thought naturally that the grease would have worn off and it has come back, however the mechanic thinks its coming from the top strut area and it wasnt intermittent last time either.

Can anyone shed any light or have any experience of a knocking noise that can be fine one day and then bad the next?

 

Not sure your car MY, mine MY98 had a similar noise but more of a 'creaking' metallic noise which was from the front drop links.

 

Could be drop links, top mount, shock absorber, wheel bearing, wish bones, track rod end, drive shaft.. there's a few options. Try jacking up that corner and check everything for play, maybe it will show up. You might have to be a bit forceful to make it happen with no load on the parts.