I'm sure the BBC's poppy-wearing gets earlier each year. There was one on the News last night. To me, this premature anticipation of the event detracts from the significance of the day itself - in the same way that people seem to be "partied-out" long before December 25th.
In the 1920s, When WW1 was well within the memory of most of the population, it was accepted practice to only wear the poppy on Armistice Day itself - a key point in one of Dorothy Sayers' "Lord Peter Wimsey" mysteries. If that's good enough for the (admittedly fictional) General Fentiman, it's good enough for me.