How infuriating.
I think we've all been there hence why this forum is here.
Ive posted somewhere earlier but go onto sky go error messages into your browser.
You will get a list of different error messages and the troubleshooting steps for each one.
At this stage, if the error messages for trouble shooting do not not quite match what you are seeing; TRY THEM ANYWAY!!
I was also at it for days and even had a microtek access my computer remotely for over an hour, and he couldn't sort it.
I stumbled on the error page at the point of giving up, and my issue turned out to be as simple as resetting the silverlight settings. I couldn't believe it.
You have nothing to lose at this stage so try them all.
Good luck.