Most distance learning providers don't offer Geography, due to the fieldwork requirements I believe. There are a small number that do, but normally it's designed to be taken over 2 years. most likely for the same reason. I imagine due to the need to undertake fieldwork, would be difficult to do within just one year as the fieldwork limits the amount of time you can spend on the rest of the curriculum (but is required, unlike labwork for sciences which is separate to the A-level exams - the Geography exams have a paper which specifically requires you to discuss your fieldwork and methods to my knowledge).