The difficulty of attributing deaths to heatwaves is something that comes up in books like freakonomics if I am not mistaken.. At any rate, from that wikipedia entry:
> Netherlands reported 400 excess deaths in the week of the heat wave, a figure comparable to those recorded during the 2006 European heat wave.
Netherlands is considerably smaller than the other nations.. Most put these spikes as a portion* that would have died in the next days weeks, or months lowering statistics later in the year and a portion that would not have.
(Edit)
A paper putting the 2003 heat-wave death toll at 70,000:
https://www.sciencedirect.com/science/article/pii/S163106910...
*The term from the 2003 paper is harvesting and there were little to no signs of it.