Has it suddenly appeared (wasn't there before)? You would have had to install the IPv6 Protocol, and i don't think you would have got it from Sky anyway unless you are direct connected (no router).
no idea, jsut done ip config as a random thing, thou i have noticed my connection speed now hitting 13mb, up from 12.5
I'm assuming you've got a router, your PC had IPv6 installed for ages (think vista installs it by default) and so that's all you are seeing. It's not from Sky, just the autoassigned IP6 address.