Your friend could try http://www.uniquelanguages.com.

There's an English school based at Dulwich College over the summer. It's not run by Dulwich but they use the facilities. There is boarding and they go on day trips too. Sorry I can't remember the name of the organisation but my friend works there every summer

A friend who lives in France is looking for a course/exchange/placement etc. for her 17y/o son to improve his English over summer. He speaks French and Dutch. They are looking for something lasting a couple of weeks and there would need to be some sort of accomodation option. Does anyone know of anything that might fit the bill?

Many thanks