Rory, call around. I had mine done by Safelite and it was pretty cheap.
Here's what happened with me:
Windshield broke and I called the insurance company. I have a $250 deductible. Got an estimate and the cost was going to be $290 or so. Basically, I would pay $250 and insurance would pay $40. I asked if the cost would be the same if I paid for without insurance. They said, "yeah, it may be less" I then called and got and estimate from a few places. I think I ended up paying $175 cash instead of having it go through insurance.
What a racket!!