Ford Galaxy steering feels like driving on ice, loss of control

I have an intermittent problem that happens in all weather conditions. It sometimes feels as though I have hit a patch of ice and don't have control of the steering very briefly, other times it feels as though someone else has tugged the steering wheel.
It has been looked at by a good garage who only found that the wheels needed re-aligning.
Then I found that it had been sold to me (12 months ago) by a car sales firm with an outstanding recall for rear suspension toe link bolts corroding which can effect steering, however the Ford main dealership have replaced the bolts this morning and did a 48 point safety check for me but not found any issues.
I am at my wits end as I really don't feel as though I trust the car now.