((((hugs)))) sorry to hear about your dad
a) He has started to refuse wind down time and as soon as I get him in his room he is not interested in stories at all. He makes the 'sleep' sign and tries to climb in his cot. This should be fine in theory but leads to..
b) once he is in the cot he then thrashes around like a little mad man. He runs up and down the length of the cot, throwing everything out and then demanding it all back. Two nights ago it took an hour and 10 mins for him to go off but there were no tears - just tooo much excitment. Then last night it took 50 mins and tonight it took 45
I think you take all of his toys out of his cot full stop - the only exception being ONE lovey if he has a special toy or blankie for sleep. Then there's nothing to throw out or demand back. You have the room completely dark - then there's a limit to how much playing he can do. I would continue with your wind-down (keep it short) and if he doesn't want to participate so be it. You can't force him to wind down, but it's important that you give him an environment in which he can wind down.
At bedtime, I would put all toys away and have dim lights and relative quiet for an hour before bedtime.
how can I start to move away from the cot?
Just start moving away. Expect tears. Sit two feet from his cot. yes he will scream and yell, just keep using your voice to reassure him, and remember that he will go to sleep eventually. Give it 2-3 nights, then move another couple of feet away. There's no magic bullet here, the only way to achieve your goal is to keep moving towards it. Of course set yourself (and him!) up for success as much as you can, but there's only so much you can do.