We stayed at Olivier's apartment during the heatwave. The flat is very well insulated, so the temperature was always very agreeable and coolish inside! Dominique was very lovely and antecipated the heatwave -- we had a huge fan to help out on the warm days.
The location of the flat is great, right in the middle of Vieux Lyon, and close to the main tourist destinations and to a metro station to get into town.