[mechman]

If I plan to use two screen types which one should I calibrate my projector on? The white screen will be used for movies where I would want the best colour reproduction but I think if I calibrated on the white the performance on the grey would be poorer? If I did it the other way round perhaps the performance on white would be more forgiving?

Calibrate both. While I don't have a Panny AE4000, most projectors usually let you save a couple of different user settings. My BenQ allows me to save 4 IIRC.

Secondly, If I want an ambient light compensating grey that will allow me to watch TV/Sport with an adequate picture quality would Black Widow be the way to go with this projector?

But of course! Nothing is more well known or more well used than Black Widow. Accept no substitute! :T