OK I have made progress. I should have followed the same procedure that works with computers - when something goes wrong, check the last thing that was changed. I jacked the car up and and rotated the front wheel with the car in gear - I could see the whole lower control arm moving backwards and forwards as I rocked the wheel :-(

I found that the clamp bolts that hold the rear lower control arm bushes in place were loose - both bolts on both sides!!!! I think the rear of each pair of bolts also holds the sway bar in place, so it was probably able to move as well. Another case of "learn to do something yourself, and then you've only got yourself to blame if it's not right". In this case I paid cash for the parts and labour, and no invoice was issued - only a hand-written quote, which I have no doubt lost.

In hindsight I should have checked everything much earlier - on the trip home from having several jobs done (inc. the bushes) the air intake pipe blew off the throttle body becasue it hadn't been tightened properly by the apprentice (it's a Turbo CT motor remember...). I also remember being disappointed that I didn't notice much improvement in the steering with the new bushes.

AllenM I did find something else that I'm sure has been an issue for the whole time I've had this car (about 4.5 yrs), and which I believe causes a bit of knocking noise - the amount of free play when I rotate the front wheels (one wheel jacked up at a time, car in gear) is considerably more on the driver's side. This does not appear to be in the CV joints, as the drive shaft rotates as much as the wheel.

So the extra free play is in the diff - does this mean it's about to explode?