I'm co-sleeping with first child, nearly 6 months old.
We have a Mothercare bedside cot, which she sometimes sleeps in - especially for the first part of the night, then ends up next to me when I fall asleep feeding.
She has a grobag, the duvet hangs mostly over DH's side of the bed and stays no higher than waist height on my side. I sleep wearing a cardigan, which keeps my top half warm and is great for bf access! At first I had to keep DD well away from DH, as he nearly knocked her when turning over in his sleep, but now he is used to turning over in the same amount of space each time, and DD is much bigger so we don't worry.
Also I use a small cushion instead of a pillow, to create lots of safe space.
When we go away we try various tactics - using furniture to block one side of the bed, DD and me sharing double on our own, etc.
I must read Three in a Bed,... but I understand a key feature of safe mother-baby sleeping is that mother forms a protective 'C' around the baby - knees brought up and arm over baby's head. It stops baby moving up or down, and prevents you from 'forgetting' baby is there and turning over. Must admit this made my arm sore after a few weeks, which is where the bedside cot came to the rescue,...
Sorry for the essay!
Wish I'd asked these questions before my baby was born,...!
Good luck - I love it