+1 for Tempur.

We've had one for 2 years, and I recommend it warmly.
In Rome it can get hot in summer (up to 40 Celsius degrees), but I never had issue with temperature, which supposedly depends on the fact that the memory foam they use is ventilated.

Depending on your weight, they will recommend specific models and related thickness. I weight 75/80 Kg, but I am positive they had different (thicker) models for people of 100Kg and above.