Nope - it's doing my head in. It must be something loose under the car as it happens only at certain revs, or when i'm driving down a cobbled street. Replaced the engine mounts during the week as they were completely rotten, hoped that was going to make a difference, but no change.
Rubbish thing is, I can pretty much guarantee that whatever it is, it's probably my own fault. I'm starting to suspect that when I took the gearbox and propshaft off to change the clutch I might not have put it all back together properly.
Might just bite the bullet and take it to a garage and let them track it down. Don't really have time at the moment to do it myself, it's exam time at uni, and even when I get an afternoon off to work on the car, I still have to be sure that it'll be back in one peice by 5.30 for work!