Hi mickb,
I found working f/t got harder and harder as my kids started to go to school.
In terms of career progression, there are many reasons for finding yourself not progressing even when you're f/t, when you've got kids. For me, inability to stay late when they need you to, inability to travel when required, their knowledge I might have to rush off if my children are ill, and so on. I can honestly say I was less focused on my career when the kids started school and I had to be here there and everywhere for them. I just wasn't the same employee - less focused, and finding work to be an inconvenience, but had to do it. Prior to having school age kids I was more dedicated.
I'm now considering what to do myself after my maternity leave, but it wont involve working f/t. If you can afford to work p/t it's a good option for the kids. I now know what the kids are doing at school, how to keep up with their homework and reading records, when such and such is happening, etc. I found it hard to keep track when I was working f/t. Also from my perspective, my kids started alsorts of afterschool activities: cubs, rainbows, swimming, even things like school discos, plays, etc., and they often all start at about 5/5:30 - difficult if you're not there. It's a very different situation when your children are at nursery - I found.
Hope this helps a little.