I like September. The cold pooling starts tentatively at the polar latitudes and the long fight back begins!
Mini heatwaves like 1991, 1998, 2003 where 25C is exceeded 'readily' as Siobhan Ryan would say. Beautiful hazy golden Octobers with temperatures in the high teens, occasionally touching 20C. Like October 1994 and 2003 for most of the country (bar hail and thunder mid month in the east). Days as late as the 19th October 1997 reaching 21C in warm sunshine, not a November moist southerly.
Let early November bring the first air frosts rather than October. Let the winter rains begin then. Let any blasts from the north and north east occur the last week of November when they are potent enough for snowfall, like 2010, rather than sleety cold northerlies in late October to mid November which only deliver to high ground and are just a waste of good synoptics for most of us.
If temperatures of 12-15C hit in too early in September, like 1992, the winter is very long. And in that particular year after a cold September and October the winter had little snow or real cold, just dark dank winter.