Frenchy and Lyes thanks very much for taking the time to respond and have a go at it.

Michael, yep I fully understand what your saying. The problem I have with creating this shape is that I'm trying to model this windscreen accurately. It is not for a fantasy object but a real aircraft. While Lyes solution at first glance seems to be a good one it is not giving me the flat windscreen that I want to achieve but a curved windscreen that follows contours of canopy shape. In the side view shown it needs be straight line and not curved. Cutting out the windscreen and sweeping it again is only restoring the original shape So Frenchy's very first post is closer to what I want to achieve (although not ideal) due to the extra flow line added to the shape associated with the sharp corner which will require lots of tidy up in the polygon mesh generated.

I guess this is just another limitation of working with nurbs, that I have to accept.