I've just finished teaching my module on Democratic Theory. When discussing the plurality run-off method, I used French presidential elections as my example, though there voting takes place in two distinct stages. It seems, however, that the London mayoral elections use the plurality run-off method, as the BBC report here:
"With no candidate set to get 50% of votes, the top two go into a second round, where the second choices of those who voted for the five eliminated candidates are reallocated."
In related news, local elections were also held in Scotland, using the STV method (see the end of this report on results or this Q&A).
Readers may remember that I backed the 'Yes to AV' campaign in our recent referendum on electoral reform. Though there are some problems with AV, I think the three main arguments that swung the referendum were: i) under AV the 'loser' wins; ii) under AV some people get more votes; and iii) AV is too complicated/expensive. I don't think any of those arguments are good ones, and the links given will take you to my rebuttals of the first two. But the interesting point is that all of those arguments apply at least as well to STV, but I don't hear anyone round here complaining about it...