Why has my steering gone funny on my ford ka, 51/01 reg?

I recently had to have both my front bushes & front tyres replaced on an MOT. Since then the car had to go back because they had'nt put any grease on the bushes, but now the steering seems very vague & sometimes unresponsive.
Sometimes when i go round an island or a bend the car just feels very light & feels like it's being driven on ice.There just seems a lack of grip that was'nt there before i had the bushes & tyres changed.
Does anyone have any idea what may be causing this.

Adam Billingham
December 2004