Good kids DVD's that are educational?

My nephew is 4 but has learning difficulties. He is lagging in some areas such as being toilet trained and speech. My sister also has two younger twins which take up a lot of her time and she even admitted that she just doesn't have the time to spend with her son that she could. She takes him to speech therapy and he goes to child care one day a week but otherwise she switches on The Wiggles and lets him watch that. I offered to teach him art a couple of hours every fortnight to give her a break and he has really taken to it. The thing is it has been 3 months now and suddenly he is learning things that he has never before. It is a suprising breakthrough for her and especially me since I am not a trained teacher. He particularly likes ons and the computer and I sit and show him how to get around kids websites etc. he is very visual and seems to relate to minute detail. He loves the Wiggles and I think they are entertaining for a while but not educational enough for him. If he had another DVD that my sister could put on for him that would actually teach him a bit more about life I think this would help him. Until he learns more unfortunatly he will not be able to go to normal school and my sister just does not have the time to spend with him. Does anyone have any suggestions about good educational DVD's? It would be better if they were Australian productions as he could relate more to them especially the accent.