Surprised it is not higher than that. Makes me wonder how the hell we managed to get 19.7c in July 2006!
It's been fresh at night, until this week. Night temps are just as important as day temps. I think the max temp anomaly will end up much higher than the mean anomaly. I remember 2006 well, and it was muggy. Look also at how Aug 1997 competed with Aug 1995 - all about night minima.
In our favour though, West is best heatwaves like this one favour the CET because all but one of the stations (Rothamsted) is in the West. It's really a WET. Those months that are warm in Kent and London but poor in the North West and the West Country do badly on the CET, like most of the summers months of 2009.
Brockley, South East London 30m asl