Dialsmavis - I had no intention of co-sleeping when DS was born. None. I was firmly convinced he was going straight into his cot in the next room (despite the advice that he should be in my room - there wasn't room in my room for a cot). Had the nursery all set up ready to go.
Then he was born at 2am, and he was given to me to cuddle - couldn't put him down. Went down to the maternity ward at about 5:30am, just as the ward started to wake up so got no sleep - kept him with me. Nightmare day trying to feed him (tonguetied baby), culminating in a migraine, me trying to discharge us both and them offering me a private room. So I stayed - and they brought a hospital plastic bassinet in for DS but he didn't like it, so he wailed - and he stopped wailing when I picked him up - so I kept him in with me. And that set the scene for when we went home. Plus I was feeding for up to 2h at a time, mostly lying in bed (only way he could get a decent latch) - so he just stayed in my bed. DH couldn't stay, he "needed his sleep" so absconded to the spare room, which made it safer - I slept in the middle of the double bed and could move DS from side to side for feeding. I am a very still sleeper but slept with my arm out above his head anyway, so I couldn't have rolled on him without breaking my shoulder.
That way we got far more sleep, I believe.
When DS was 5.5m, we started to disturb each other's sleep and that's when I moved him into a cot - but if during a night feed in his room, I started to nod off, I brought him back to my bed again - much safer than risking falling asleep in the chair with him.