I'm not familiar with shared ownership, but with affordable housing it is generally dependent on what the banks will give you. Maybe it would be an idea to get approval in principle from a bank and then approach the councils? If you have a few good years history with revenue I would have thought that would be proof enough. I know people who were refused and wrote letters and got their property. My advice would be to gather your documentation and don't take no for an answer if you know you have regular income.