More than a language holiday, a life experience. I travelled to London for 3 months. It was the first time there and my level of English really left a lot to be desired: needless to say I was both impatient and anxious. In the end, I was more shaken up than hurt because you meet incredible people very quickly, the classes are adapted to each level and nobody judges you, because we are all in the same boat!
In addition, the school organises a social programme (restaurant, museum visits, activities, etc.) to show you around the city, so you never get bored! It comes without saying that London is a very active city with lots of things to discover, monuments, art, shopping, the Queen, let alone a few pubs.
To conclude, I think such an experience teaches you a lot about the language, which is the primary goal, but also about being independent and managing yourself. I strongly recommend it and if I could, I would go back there as soon as I can!