That's in line with other estimates. Two things to keep in mind:

1. If you follow that wikipedia link to here, you'll see that most of the WWI civilian deaths were due to "famine, disease, and accidents." in WWI, the German submarine campaign caused real hardship to the British in a way that it never quite did in WWII.

2. The Blitz, for all its fame, was not as deadly as one might suppose; the Germans never had the resources, or the command of the air, to do what the Allies did later in the war to Hamburg or Dresden.

Here's Churchill, talking about the raids on London once it was clear that the Germans were going all-out (October 8, 1940):

[T]he deadliness of attack in this war appears to be only one-thirteenth of that of 1914-1918. [he meant deaths per ton of bombs, which he attributed to good shelters]

Whereas, when we entered the war at the call of duty and honour, we expected to sustain losses which might amount to 3,000 killed in a single night and 12,000 wounded, night after night, and made hospital arrangements on the basis of 250,000 casualties as a first provision--whereas that is what we did at the beginning of the war, we have actually had, since it began, up to last Saturday, as a result of air bombing, about 8,500 killed and 13,000 wounded. This shows that things to not always turn out as badly as one expects. . . . since the heavy raiding began on September 7, the figures of killed and seriously wounded have declined steadily week by week . . . .

We must not exaggerate the material damage which has been done. . . . Statisticians may amuse themselves by calculating that after making allowances for the law of diminishing returns, through the same house being struck twice or three times over, it would take ten years at the present rate, for half of London to be demolished. After that, of course, progress would be much slower.

Source: A book of Churchill's war speeches; I don't have an online source.