Joking aside, I think a predictable consequence of the #UKSocialMediaBan is that kids (and others) WILL use VPNs to skirt the ban, and that carries significant risks.
First up, government action to control/outlaw VPNs. It's in the nature of governments to make poorly thought-out laws about tech and then, when someone does a technological end-run around them, start playing whack-a-mole to try to get the genie back into the bottle. Never works, but they do it anyway.
1/