New to the site and this forum but have been putting a few things together myself after reading all this fabulous thread.
In the evidence trail concerning Greg's statement to police, it appears not to be about the attack by Tony but much earlier in his life, and both Tony and Emily appear to have been present at the incident. Even more strangely Emily is " Emily Hughes" in the details. Given that it appears they were teenagers in this statement it's unlikely she was married to Tony at that time. Does this suggest they are actually brother and sister? Or related in some way?
It also shows they have known Greg for a long time, at least since they were teens, could he then have been paid to father a child for them? is that what the pay off was about? Is that why Tony attacked him?
Is it also why Tony's parents never appear after Ollies disappearance? Because Emily's parents are his parents too?
Is Ollie actually not Tony's son, but has been paid for, and for some reason Greg decides to take his revenge and take Ollie?
When Emily's father needs a place in a hospice Greg finds it for him, so the father is indebted to him for this. When the father mistakes James for Ollie at his bedside is this infact because Ollie is at the hospice with Greg and the father has kept his silence because he now owes Greg?
All theories, and probably way off, but you never know...