LostinLondon, my DS's friends older brother was offered the same at W three years ago, but they had no choice and he joined W. Their DS received the same extra care and attention as other scholars.
Last year W awarded him with a reduction, the main reason being that he is now one of their top boys at his sport and has risen very fast into county level. My friend says that the school claims they could see the potential but as he was not academy/county level at that stage they were unable to offer a %. My friend was very bitter at first but they focussed on making sure he made it and that W ate some humble pie! Which they have to an extent. But to be fair to W they did give the boy extra help, support and mentoring and also opened up the door for him to walk through.
Although my DS is at an academy the costs of travelling around watching him train and play pretty much offsets the value of the scholarship. I just phone DH and he said to accept the offer and move on.. hmmmm men.