Hi Dan,
yes, you'll need somewhere warmer than your garage for fermentation and conditioning - too cold and the yeast goes to sleep, to hot and they might get killed off. Most homebrew yeasts are happy enough between 18 - 24 degrees, and its best to keep your brew somewhere where the temperature is in that range and pretty stable. If you have to keep your fermenter in the garage then there are options for heating it (brew belt, water bath with an aquarium heater, heat pads) but I find i easiest to keep my beers in a nicely centrally heated house during the fermentation and warm conditioning phases. Once the beer has been bottled and kept in the warm for a couple of weeks your garage will be ideal for cold conditioning, the final stage of letting the beer settle before its ready for drinking.
And if Thornbridge beers float your boat, try the Festival Razorback, which is fairly close to a Kipling, or Youngs American Amber ale, which isn't a million miles away from a Sequoia. I mainly do all grain now, but still do these kits regularly to keep stocks up! (The homebrew shop on Abbey Lane sells both - they are premium kits so a bit more expensive than some, but well worth it IMO).
Good luck!