Children are effectively allowed to access porn. This law will ensure that there is some of it that CAN'T access, just as children CAN'T buy tobacco products
This law will be so ineffective as to make no difference. I really can't go any further with this aspect of the debate if you honestly think this will work in any sort of meaningful way.
Furthermore, the smoking ban did reinforce the idea that smoking is NOT entirely ok for adults to do
Yep, that's my point. That law was effective. It was well thought out, it was enforceable, it was preceded by campaigns and combined with other measures.
Similarly this law could strongly suggest that porn is something elicit and regulated as opposed to being open to all
Maybe, but I doubt it. Much like the extreme porn laws it has had little fan fair and that certainly hasn't been the message the politicians introducing it have tried to put across.
Adults will have to give their credit card details and risk fraud
No they wont.
What law would you suggest in its' place?
I am fine with this law as part of wider measures and a wider campaign if that's what it was. I would change the way it was announced get loud cross-party support, have a media blitz with womens/childrens/trafficking charitites supporting it. I would combine it with adverts about the dangers and effects of porn, a ban on talking about or alluding to porn pre watershed, I would bring extreme porn laws in line with this one (ie not just enforced against UK producers), I would also review those extreme porn laws because at the moment they seem rather odd. I would commission proper research on porn, its contents and its producers in order to create some targetted (evidence based) harm reduction and education. It would be part of a long term strategy.