Scotlandspeople discusses the legal age issue, as they changed it around the same time as England & Wales... and the reasoning would probably be the same:
Basically, although it was technically legal to marry at 14 for boys and 12 for girls with parental consent, people had long since abandoned the practice (and even when it was done, it tended to be amongst the landed gentry in order to merge/reunite property & wealth).
For many generations it was one of those ridiculous laws that people didn't actually take advantage of, and it was changed so late because it wasn't posing moral problem in society (ie it never cropped up as an issue).... had people been regularly taking advantage of the legal right to marry at such a young age, they would've changed the law at a much earlier stage.
I'm not saying it's impossible, but when ancestors look like they may have been married so young... consider the other possibilities, as those are probably more likely... son/dau-in-law so young will probably be a step-child or other dependant.
I have around 3500 names in my tree from about 1570-present, and never once found a marriage below the age of 16.