The 3 hot days here had maxima of 31.4, 31.4 and 31.5. These are the latest in the year that I have recorded 31°C. However, a max of 30.8°C was recorded on 13 September 2016, a rather isolated hot day. (Record starts 1983).
Tudor Hughes, Warlingham, NE Surrey, 557 ft, 170 m.