Not really possible to value the individual clubs but I think we can safely assume that City represent a large part of that £2bn. I don't know what ADUG would do but other investors are certainly a possibility and, as you say, we could sell another 12% without ADUG ceding overall control. India is another market where there is huge development potential for example.
I remember the days when Sky had a stake of 10% that they'd forgotten about and would have taken less than £2m for. That valued us at around £20m whereas today it's £2bn.