The SuperRoubaix material is quite fleecy on the inside and is much thicker than just regular, lycra tights. It will be quite warm enough while your moving along although I kind of agree that wool would be a good choice for you. Actually I think wool would be more expensive though. Netti is a good Australian company that sells lots of different cycling gear including SuperRoubaix tights and bibtights.
I guess it depends on what you call expensive. I think tights from Netti go for $80-$90 and bibtights are about $140. If your not signed up for eBay get yourself an account and start looking there. You can get good clothes for decent prices there if you look around and sellers will post it to you.
You WILL have trouble trying this gear on though. I live in Canberra and I can't stand putting on full winter gear in summer. Up it Tully it will be completely unbearable. You may have use someone's coolroom to try on any of this gear.
Anthony