I am an American who has been living in London for 15 years durign which time the misuse of "sat", "stood" a so forth has become pandemic, used by virtually everyone nowadays -- from laypeople to radio and television presenters and even BBC reporters. In my time here it has got much worse, as, at first, it seemed to me to be more a Northern colloquialism. It is decidedly shameful that it has so quickly become the established form.