Hmmm.......... As a concerned 14 year old I have to say that this won't make the slightest bit of difference.
People like me will always find ways to get the games they want, and I'm sure that stores that already don't sell these games to minors won't change their ways simply because of an age old clerical error on the behalf of the U.K Government, who have demonstrated time and time again that they have an extremely limited grasp of how to actually run a country.
There will always be those game stores that actually risk selling to underage customers, just like there will always be stores who enforce the laws even if they don't apply anymore. A reasonably intelligent teen will almost always be able to tell the difference between the two, and while it may take a little more effort, a little more time, they will eventually get hold of what they want.
Of course, this only applies for those of us who know that a little respect for the store staff, and not showing up dressed like we're about to go tag someone's property goes a long way towards being treated like people, instead of what are basically considered verminous pests (ie. the average teenager).
Just an FYI: Did you know that the government once introduced devices that broadcast irritating noises at frequencies above what the adult human can hear, but just within the audible range of teenagers to prevent teens from hanging around in front of stores?
Then of course they realised that this would also affect young children and babies, so it was removed and outlawed........ Really opens your eyes when you realise that society treats ALL teens as pests, no matter what they are actually like, and only react to obvious breaches of civil rights like this when they realise that the "innocent" younger children will be affected, giving no thought to the just as innocent teenage bystanders.
Of course, the sad irony is that it is actually this kind of treatment that prompts most teens into becoming the very thing society expects them to be; dangerous pests to be exterminated.
