If I keep the car (Ka) driving in a straight line or through a slight bend without the suspension loaded it up, give it a touch of throttle and it will change lanes on its own, no clunk, no warning, after turning the PAS pump off it still does it, any ideas of what it could be?

I've had issues with the bottom arm bushes popping out after a couple of days from new but it's never behaved like this, it's downright dangerous

I was MOT'd a few weeks ago with no advisory on suspension/steering etc