Where can I get a rescue dog for the disabled?

My husband and I live in a lovely house in the countryside with our little boy, and have decided that it's time now for us to get a dog. We want to get a rescue dog, for obvious reasons, and a few years back I met a lady who worked for a dogs for the disabled charity. She told me that they often have dogs who have either failed the training or are considered too old to work anymore. We feel that highly trained dog like this would be ideal for us however I no longer know the number of the charity she worked for. Can anyone give me a lead to a similar charity? We live in Hampshire (UK).