Parts for a Window Regulator - 2004 Megane?

I need a passenger rear window regulator - bought my car from Bristol Street Motor Nation (Never will again) in Darlington and they say the window will have never worked as the regulator in the car isnt the right one - and it has been changed - but it hasnt !! Anyone know where I can get the part at a reasonable cost as they are quoting me £200 minimum excluding VAT, labour etc