hello helen. firstly it could be anything such as bottom ball joint, cv joint, wishbone bushes, track rod end. your best bet is to get it checked out asap. CONTINUING TO DRIVE THIS IS DANGEROUS. this is because something could break while you are driving causing you or the driver to lose control. if you do get someone to identify the problem, you can buy the relavant part from a discount auto centre such as EURO CAR PARTS, HALFORDS, DISCOUNT AUTO PARTS etc.this will save you money rather than buy from main dealers. for fitting someone could charge you from £50 to £100 approx. i hope this helps you. good luck.
shaffick
December 2008