False alarm. My sincere apologies.

Turns out the rules haven't changed in terms of taxation, it's more of a data sharing process that's changed

https://www.tax.service.gov.uk/guidance/check-non-paye-income/outcome/sales/you-do-not-need-to-tell-hmrc-about-personal-possessions-no-profit

I stand corrected, and am now deleting this link, along with my sincere apologies for wasting anyone's time!