Back to Work - Should I Stay or Should I Go?

 "Are you going back to work?" The BIG question that I seem to be asked regularly now that Marny is 6 months old. The going back to work topic is everywhere I go and Mummy's all around me are asking themselves and each other "Should I stay or Should I go?"
 In my case financial necessity means that I need to go back to work part time and actually dare I say it I believe that my sanity requires it! As I sit here trying to work out the Maths I have found a problem, one that I am struggling solve. Part time, is it worth it? Your responsibilities at home vs part time low paid work. If you take into account all the money you pay out just to go to work - childcare, travel expenses, work clothes and lunches not to mention the emotional cost of juggling work and home life.
So I have decided that I need to make returning to work worth while and I am not just talking financially, I need a job that takes away the pangs of guilt, you know the ones! I need to feel that I am doing something worth while, I need to be brave and look for something new but what and how will I find it? Am I just getting caught up in this 'have it all' culture?
So my question to you is "how do you find the work vs home balance and if you have returned to work, have you change direction since having your little one?"