Hi - we are planning to travel through Nanning on 19th April 2014 with the possibility of staying for 2 nights the focus being to photograph the De Tian Falls.

Have located an overnight train from NN (leaves 6.15pm) to Ha Noi (arrives 7am) - perfect (China Rail)
Still checking accommodation at the DeTian Falls

Hi, Detian Waterfall is around 250km from NN city. U can take a bus at Langdong Bus Station to Daxin County and then transfer to another bus to get there directly. I know there is a Daxin Detian Resort Hotel, just next to the waterfall, where you can stay for a night.

Apart from the train you have searched, there are also buses from NN to Hanoi, which can be taken at Langdong Bus Station.