Tired of pottering about the garden, watching daytime telly and staring folornly at City Hall, Ken Livingstone has found himself a retirement job: hosting a phone-in on London's LBC 97.3 radio. Like a Frasier for London, Ken will apply his knowledge of the City gleaned from many years in office to debate with, educate and probably rant at callers to the show. How London's cabbies (who seem to have LBC hard-wired into their radios)......