Gentlemen, many thanks, most enlightening.
My only mystery is when man-service GCB chevrons ceased to be worn ......... definitely still on show in WW II.
May I make a pedantic point and then wind my neck in?
CHEVRON is point up [French, as in the pointy things holding up a roof] in heraldry and therefore in badges. However, given that official documents often revert to "stripes" there is no point [see what I did there?] in labouring the chevron theme.