In regard to the last post, I think it is important to note that 'active' parental consent was not necessary for those under 21, AFTER the calling of banns. If parental dissent was not raised during the calling of the banns, in the period up to the ceremony itself, then any marriage that went ahead was valid. Only if the ceremony proceeded following active dissent was the marriage invalidated and the clergyman (afer 1754), liable to transportation.
Therefore, those such as orphans, or who eloped and had the banns called away from the the notice of their parents could and did marry earlier and the marriage was valid. (Source: 'Marriage law for Genealogists the definitive guide', Rebecca Probert, 2012, Kenilworth: Takeaway (Publishing)).