I would sort of recommend the Dulwich Riding School if going further out of Dulwich is not an option for you. My daughter has had individual lessons there for a couple of years, and, although the tuition was a bit hit and miss, she mostly had good instructors and she has learned quite a lot. The best option is to ask for a semi-private lesson, either with a friend, or with somebody else. Very often it has happened that they did not have another person to go along, and she ended up having a private lesson, but at less cost. The management of the stables are a bit gruff, but when you get to know them they are OK. They only tend to ride out in the park at quiet times, and it is true that they rarely allow the horses to canter, although it does happen. Another option would be the stables at Mottingham, which we also have used. The riding there is a bit more satisfying because they have some land, and the teaching is usually good.