Just measured my original Matchbox (45A) at 57.75mm long. 167" is about 4242mm, so the scale is about 1:73.45.
Perhaps someone in Vauxhall's management realised FA perhaps wasn't the best of codenames, so these were always referred to as F, series I and II (though the final 1960-'61 model had some significant revisions, including a completely new, higher rear window and roofline but wasn't called series III). I still need to build an FE to complete the line-up.