There is now a green screen on the wall in the back. Please feel free to use it.
It’s basically some sheets of plastic, painted with matt green paint that was lying around in the space. It has been tested with a Samsung Galaxy Note 3 camera and iPhoto and it blends seamlessly. No shadows or marks blended into the final product.
To get the best results use a good quality digital camera that doesn’t bleed colours. Using an old JVC DV tape camera from 2004 which bled around the edges left a halo in the final product. A still camera with movie facility with automatic exposure settings totally messed up the green screen effect.
And here are the results.