Thank you Lusodancer! My plans have progressed and we are actually moving.
I am not necessarily looking for London only but rather, a school that offers a high school "degree" - which I take to be an "upper school diploma" or Sixth form (please correct me if I am wrong!). My employer will actually pay her tuition if I can get her into one of those - yes the WHOLE boarding and tuition. She is a pretty strong classically trained dancer who has either attended or got accepted into some of the "big" US summer intensives (incl. ABT NYC, PNB, Boston, Houston, Ellison) but having said that, she is not one of the rail thin ones who was selected to do the Royal Ballet Upper school after doing the White Lodge program last summer. Her goal is to dance professionally and because we have both EU and US citizenship, she is eager to try Europe.
I have a list of schools that I think go into this category:
ENBS
Tring
Elmhurst
Central
Russian?
If anyone knows of any more of them, please let me know! Also, if you know of any "full academic schools" across the pond in EU let me know. The Danish and Swedish I think would qualify but other than that I am not sure.