Watch this vid:
Pressure marks on leather -- Leather Care -- www.colourlock.com - YouTube
Tip: be GENTLE with the heat - massage the Christ out of it. I've had great success with this technique, avoid chemicals etc etc
After you're happy with results - get some conditioner on those seats, they look dry/tight. Best way to think of leather is human skin, keep it moisturised as this helps to keep it soft and flexible!