The Whirlpool reversible mobile air conditioner has a 23% discount at Boulanger. It can be used both in summer to cool a room, and in winter to heat it.
The device can also be used in heating mode, but also in dehumidifier mode if needed. The best offer to grab is Cookeo Moulinex Cookeo Touch Wifi at 399€99 instead of 449€99. You can buy a caulking kit, sold separately, to optimize your installation and ensure you enjoy controlled freshness.