You should find that most cars with automatic climate control where you can set a specific temperature will allow you to go down to 16 or 17 degrees, as well as a 'low' setting that sets the fan speed to maximum at the lowest possible temperature. You should find this cold enough for almost any situation.

As for comfortable seats, as a general rule larger cars tend to have more comfortable seats as the size of the car means bigger, more comfortable seats are fitted. You don't mention your budget, but we'd be looking at cars like the Skoda Superb or Volvo S90/V90 for maximum seating comfort and cold air con.