Even though I’ve just had a replacement steering gearbox fitted, the handling still isn’t right. It is definitely an improvement, in that the steering feels a lot smoother, whereas the old one used to have the occasional dead spot where power assistance used to drop off.
My theory now is that the problem is at the rear of the car. Maybe the shocks? They are LAD shocks though, so replacing them is not going to be cheap. It might be that the bushes on the pivot points of the trailing arms have worn, allowing the wheels to change their angle slightly. More investigation is needed…