Sevenoaks School in Kent (UK) does a really good IB summer revision course. You can cover two subjects in a week, but I only did Physics over three days. I found it really good, and many people who had also attended the OSC course seemed to think that Sevenoaks focused more on work and less on socializing, which I think is a plus when you're paying that kind of money.
But at the end of the day these revision courses are really what you make of them. You can ass about all day or work hard and pay attention in classes - it's really up to you. The teacher's coursework advice helped IMMENSELY for both me and my class, which was where my school was lacking. I was also able to attend talks about personal statements and discuss my extended essay individually with a teacher. The physics teacher was also one of the people who writes the physics papers.
As much as these courses are about going over revision material, they are also about getting the most from your teachers. Asking for advice, handing in courseworks so that they can mark them and provide advice etc. You can always revise on your own at home otherwise. I also wanted to have a nice social experience, which I definitely got.