Wiggy - I'm hard-pressed to find any accuracy in the quoted figures for the tonnage of German bombs dropped on Britain during WW2.
The site below gives these seemingly official figures ...
Tonnage of Bombs on British Targets 1940-1945*
..1940 .... 1941 .... 1942 ... 1943 ... 1944 .. 1945
36,844 .. 21,858 .. 3,260 .. 2,298 .. 9,151 .. 761
* includes V-weapons
https://humanities.exeter.ac.uk/medi...OF_BRITAIN.pdf
The Express article below, says ...
"50,000 tonnes of high-explosive bombs and 110,000 tons of incendiary bombs (were dropped during the Blitz)".
The Express also details how around 10% of German bombs failed to go off - but ...
"Brave bomb disposal units successfully dealt with 40,000 unexploded bombs, with 750 of their own number perishing while trying to defuse the devices."
That figure would seem to indicate that London and Britain in general doesn't have too many WW2 UXB's left, to worry about.
40 facts about the 1940 bombings of WW2 | History | News | Express.co.uk
The History Place states "18000 tons (of bombs, were dropped) during 8 mths of the Blitz .."
The History Place - World War II in Europe Timeline: The Blitz
I think this article from the Independent below, could have the figures (and the comparisons), pretty right. Their total tonnage number jells with the University of Exeter figures, listed by year, above.
"The Luftwaffe's total of 74,000 tons of bombs dropped on Britain, was utterly eclipsed by the nearly two million tons dropped by RAF Bomber Command and the US 8th Air Force by the end of the war in 1945".
Germany's bombs set our cities and homes alight, but we carried on | The Independent
On that basis, Londoners have a vastly lower chance of finding a leftover WW2 bomb in their city, as compared to many German cities.