Is selling natural hair (extensions) in Britain unlawful (haram) or lawful (halal), and what is the ruling on the money earned from it if it is unlawful, considering that it has been the sole source of livelihood for seven years?

It is not permissible to sell human hair, as a sign of respect for human dignity. If someone did so out of ignorance, there is no blame upon them, and the money they earned is lawful for them. However, if someone was aware of the prohibition, they must dispose of the money by spending it on the welfare of Muslims or giving it to the poor. They may take from it an amount sufficient for their needs or as capital for a lawful endeavor.