My 2cents on Flights...
I booked and paid for my flights in Mid November (ie i got my monthly pay on the 15th) for an end of Feb departure. I got a $998 rtn fare with Qantas. I thought i was going to miss out on a fare that cheap and was freaking out.
The other thing with flying Qantas is that you can access the JAL Visit Japan domestic fares. You must book this with a Travel Agent in conjunction with your International flight. So don't book online! And I had to push and hunt to find a travel agent who knew what I was talking about. each sector/leg is 10,000 yen.
http://www.jal.co.jp/yokosojapan/. So the return flight Narita to Sapporo was $350 (give or take)
I can't for the life of me figure out how to get this fare using Jetpoo - so sometimes when you add in the domestic legs in Japan your Jetpoo cheap flight doesn't look that cheap.
On Accom I agree with TJ and think you guys should look at serviced apartments. Our first week we stayed at Hokkiado Tracks (and so did Clax I think) and could not fault them. I have a business card from one of the guys and had told them about the Shred. I am happy to email him for you guys and see what he can offer