Hi agentdark, I'm glad you enjoyed the renders : P
My lighting workflow consists of only HDRIs, usually Peter Guthrie's. For this particular scene I ended up desaturating it a bit though to match a more wintery type of light.
I sometimes also use Corona's sun and sky and I have to say that I really enjoy it.
What I wanted was to create some contrast between the cold white from outside and the overall warm light being shed in the interior from the fireplace, thus enhancing its presence.
As for the fire I had created it in the scene but ended up doing it in post because it looked better.
If you have any more questions I'll be glad to answer them.
Cheers !