Uwot m8??!!
I'm not getting you, Myster. I always presumed that Ralph died sitting in the chair, his body was knocked to the floor when police forced the door, and they picked him up and perched him, placing his head in the scuttle to collect the blood.
I need to watch The Big Bang. I'm sorry if I'm annoying you!
Nevill might not have been sitting in the chair at all when the TFU broke in, unless there is definitely a written statement saying he was.
If he was standing when assaulted, his pyjama pants (which were found around his lower legs) could have dropped down (either because the waist elastic was a loose fit or the tie cord had come undone) so it's possible that he was tripped up by them and overbalanced. If your pants are half down your leg then it reduces your ability to move about easily, even without having any injuries to slow you up.
Under a rain of blows from a rifle barrel or butt, with a fractured left arm, a bruised right arm from trying to defend oneself, and a badly shattered jaw it would have been difficult to concentrate on keeping upright, IMO.
If he didn't then fall onto the overturned chair by himself, he might have been deliberately pushed down onto it by Bamber, making the final four head shots easier to place.