It's all been delayed again (probably NSFW)
The word on the web is that it's been delayed again.
https://www.pinknews.co.uk/2019/03/27/porn-age-verification-law-delayed-days-before/
or
https://www.frolicme.com/news/further-delay-to-uk-governments-age-verification/ (this site is NSFW)
Whether it's just been delayed with no intention of changing anything & just allowing the industry to come up with products or whether they are re-opening some sort of discussion isn't clear, but the person who pointed me to this delay suggested that the DCMS are finally asking questions they've not been prepared to talk about before.