Happy to report that I have finally finished a green screen scene! It is the second scene in the sequence; a mid shot with Steve, Rob and Alex in it. Lasts all of 56 frames.
In the end I used a combination of Primatte, KeyLight, KeyChew, Travelling mattes, Saphire Edge Blur and Mocha Pro tracked mattes to key out the green.
I have done some despill work using a track matte and a hue node to clear up green on the back of the iPad.
To grade it I have desaturated the actors slightly and used a Saphire Glow node to help match the background exposure - works well and will be using the same 'recipe' on the rest....which there is loads more of!
But at least I am on my way which is such a relief.