Thanks for all your replies, I wanted to wait until the baby arrived (its a boy) to let you know how things worked out.
I took the cat to the vet as some of you suggested and she is having frontline for fleas which may have been adding to the bald patch problem. The vet also gave her some hormones to mellow her out and a month into having the baby she seems fine. The cat was on the sofa in the front room all the time I was in labour and only left at the end when the baby arrived. I have been really careful to make a fuss of her and not panic if she goes too near the baby who is now a month old.
The cat is back sleeping at the foot of the bed, and the baby sleeps with us at the top, so far so good but I do want to wean her off the hormones soon as there is a risk of breast lumps with them. She has worked out that I am an easly target for a lot of strokes and fuss when I am breastfeeding too, the only trouble there is that she sometimes tries to stand on the baby to get closer to me.
Thanks everyone for your help and ideas, it looks like it might be working!