If you're in the UK or Europe (AFAIK, this applies to Europe too), by law, any company has to seriously consider requests for flexible working (e.g. part-time hours). I simply asked, and they said "yeah, OK". Obviously working 20% less hours means 20% less pay and holidays.

I work for an out-sourcing and consulting mega-corp - I get to work on interesting projects, but and honestly, it's a horrible company to work for in terms of culture, power struggles, biases, bureaucracy and lay-offs. I plan on getting out soon, going full-time on my side business. As such, I'd never recommend them to anyone.