This string may be getting a bit stale and so perhaps this comment will disappear into nothingness, but you guys are kidding, right ? You really believe that the English don't lisp more commonly than others ?
While I agree that Marat's original psychoanalysis of the lisp is a bit much, what is obvious is that the English lisp (broadly defined as both the sibilant 's' and the replacement of 'r' with 'w') is very common, and it is an indicia of upper-class membership. This is a total no-brainer. The fact that brits fail to see this is further evidence that they remain mired in a class hierarchy the manifestations of which remain invisible to them much of the time. (By the way, isn't everyone excited by the upcoming Wedding of the Century! )
You really think the prevalence of lisps in English public figures is just about greater "tolerance" for difference ? Not a chance - the above comment about the Castilian lisp is far more to the point.
I am a mere colonial (just call me Captain Canada) with all of the limitations that implies; but really folks, you need to stop pretending about these things (though no doubt there can be charm even in such pretence). There's nothing much wrong with a class lisp (at least from my perspective as an outsider), so why the denial ?
Try this link as an example - http://video.ft.com/v/901495886001/INET-Conference-Simon-Johnson
As you can see, Gillian Tett at the FT does yeoman's work in the class lisp category - the lisp, with its implied aloofness, plus her plentiful brains, above average good looks and conversational warmth definitely make for a high hotness quotient. As the man said, it's all good - lisp all you like. (Who was she interviewing again?)
Carry on then... back to enjoying lashes and lashes of ginger beer. (Let's do pretend none of this happened, shall we?)