Wow! I ride at 1:30 in the morning home from work and the temp has dropped into the low 30's (under 5 but above 0 C).
If your fingers are doing that I would consider electric gloves or grips. I've never used them so I don't know the cost or how they work.
I rode this morning and it was 18 degrees, bitterly cold, especially at 60 mph!! The ONLY part of my body that was cold was my fingers as I put some hand warmers in my gloves. My fingers actually got so cold that I could barely operate the brakes and they started to physically hurt they were so cold.
Stig, I REALLY like the looks of those mits! I doubt I'll end up buying those or better gloves though since it rarely gets down below 20 degrees here. The last time it got down that cold was February of 2011.