I just bought the Lava motorised wall mount from RS100 which is excellent. See:
http://www.rs100.co.uk/product_info.php?products_id=563.
I am extremely pleased with this product. It works like a charm and has the added advantage of making cabling a lot easier. You can just swing the screen out and connect up as desired then return the screen to the flat position.
Also, we have our screen where we are subject to reflections from a window, however, a slight adjustment to the screen can reduce the reflections present which is great.
The motor is very quiet in operation and the ability to adjust pitch of the mount allows the mount to overcome walls which aren't particularly vertical!
Found that perhaps 3 people may be required for larger screens as it can be awkward to hook the mount plus screen onto the wall fixings. Also, if it were also available in black, that would be nice. Although I guess it could quite easily be painted, hmmm... wish I had painted it before mounting!