To be honest even a small terrace house will be £8 minimum, usually 4 front and back, thats at a £1 a window.
Depends how specific you price with bay windows, big and small windows, then there conserventories, depending on if you do just the sides, or top and sides.
I havn't really posted much on here, but been on here a good few months, anything you need to find out have a search first, there's definately 100's of comments on pricing, and they are worth reading.