No matter what job I have had I have always kept separate work wear and casual wear - even school and student days saw me getting changed when I got home, so it's a life time habit.
I live in jeans and tops when I'm not working, but my going out clothes, 'formal' stuff and working wardrobe are interchangable.
When it comes to lingerie I have separate stuff, though I would wear work lingerie if I should go out on the pull (thats been a long time since), 'off duty' I wear t-shirt bras and cotton shorts or briefs - comfort is king!