I had a new one fitted recently for £120 all in.It was the cheapest i could find in my area.
Be aware that the cheaper you get may not always be the best deal.Screens are laminated and the cheaper one's can fog up in time as they are of inferior quality."Pilkington" is a reasonable make.
Mine had chips but was still MOT passable,i just decided it was time for a new one.
This may help you decide if it's still MOT legal :-
http://www.theaa.com/motoring_advice/safety/windscreen-vision-safety.html (scroll down).
If you draw a line top to bottom on the outside ,in line with your steering column.Draw another line 145mm either side of the first one.If you have any chips or cracks in the area between the two outer lines that measure over 10mm it will fail an MOT.