Interesting question Ruth.
Thinking back a few years to the last time I was in a 'proper' job working f/t for one company, I do think if I'd been there still and had asked for p/t after having DS, they would have accommodated me.
But they were fairly forward-looking and family-friendly as an organisation and there were several senior female employees with various part time arrangements so it wouldn't have been at all unusual.
I actually think, reflecting on it, that I would have hesitated had I been more junior. I think actually in that organisation at least, being senior, female, and more 'known' and 'proved' would have made it much easier. I'm not so sure that more junior employees would have been successful in a request for part time employment. I might be doing them an injustice saying that, but with the culture there was, I think that might have been the case. Very much about individual 'stars' being important and nourished.
Thinking further back to the organisation I was with previously, again, I definitely would have felt comfortable asking. My boss at the time had an arrangement to leave early to collect her son, and an administrator in the department working part time after having a baby as well.
So much to do with where someone is working I guess I am saying!
I've just read that back, and it doesn't read particularly well but I've got a headache and can't be bothered to change it!