I only learned about ERF seats from MN, and only when I started researching the next seat for dd (now three). I know one person who also ERFs, and it was me that told her about it.
Everyone else I know turns their little ones forward facing once they get to 9 months (some, sadly, do it earlier).
ERF is so so under promoted, and the seats are so so expensive (due to lack of demand due to people simply.not kniwing they exist), that the only thing that will make ERF the norm in the UK is a law change.