I was going to get a belt when i first got my kit together, i am now glad i saved the money, the lowest temperature in my kitchen (where i have my DJ's) was 15c in the coldest part of last winter, it is now at 25c.
I was a bit worried when i started out and the average temperature in my kitchen was 18c that it was not going to ferment, i was advised in this forum that a lower temperature can actually be a good thing as the fermentation takes a little longer and is beneficial to the wine, i have never had a fermentation stop or stop early even at temperatures as low as 15c.