What would people recommend as a basic lighting setup for headshots for under £100?

My friend has asked me to take headshots of her and some people from her company. I'm only a hobbyist photographer, and have never done any studio-style photography, and have no lighting equipment at all. I think we'll be taking headshots against a white wall and a black wall. Can anyone recommend any cheap lighting setups? DIY options are also good via /r/photography http://ift.tt/2xkvNF6