Growing up.

My little man is growing up so much. I can ask him to bring me his socks and will let me put them on.
He lets me know when he's thirsty by pointing to his cup (ok ok, its still his bottle, but we'll move to a cup soon, don't harass me)
When he is given something to eat or drink, he;ll plonk himself down on the floor and wait. Oh and then jumps straight up, but you get the picture.

Problem area is changing the nappy! I know this is a common problem. He won't lie down, he won't be held down. I put him on his back, hold his ankles and then I feel I'll give him a spiral fracture of his leg bones the way he twists and turns. Very frustrating... any tips??