Political trolls are so boringly ignorant of common sense.

Magna Carta is the basis for every constitution that ever was written, it just isnt called constitution, because, well, the word didnt exist back then. Back then, it was called a charter. (Carta, in latin)

It has been reformed countless times, but like Theseus's ship, it is still the basis for all constitutional legislation in the UK.

The fact other contries have a single document called "the constitution" (which is never the only document in this country constitutional legislation) is due to the fact that once, someone refered to the many texts of England's government law as what "constitute" the covenant between people, government and the Crown, henceforth called the constitution.

You are arguing for the sake of arguing and frankly grasping at straws by holding to subtle technicalities you dont really understand.