I was at this stage last January. Build a tent out of plastic sheeting and use a space heater (fan, not radiator) to keep the temperature up to 70F or so. I got fancy with an Omega controller and solid state relays and platinum RTD sensors, but the thermostat built into the heater should be more than sufficient. I was monitoring the temperature remotely and needed to see the display via webcam because I’m a geek.