I only work 9-10hrs a day, sometimes more often than not, on a Friday I'll do around 8hrs - I like to leave early on a Friday so try and leave by 5pm at the latest
So quite happy with my work hours - life's pretty good
My contract says a minimum of 40hrs, but work is so flexible with my life and I get so many perks with work, that I don't mind putting a bit of extra effort in, and I actually enjoy being at work.

If I can do a bit of extra work meaning I can leave early later in the week, then so be it.
I'm no longer at work for 730, I stroll in around 820am now, meaning I have a lie till 645

Life is GOOD!
Ultimately, as long as I get my work done, I don't feel obliged to stay - I stay because I like to get ahead on work for making my own life easier.

I don't get paid overtime, but that doesn't bother me.