The proximate cause was a proposal by Sue Rabbitt Roff, a senior research fellow at the University of Dundee, in the BMJ: "We should consider paying kidney donors."
Her proposal calls for a tightly regulated system with a standard payment to donors of around the current average Scottish salary (at which price transplantation is still a bargain compared to dialysis).
She concludes "So it’s time to begin to explore how to pilot paid provision of live kidneys in the UK under strict rules of access and equity. We need to extend our thinking beyond opt-in and opt-out to looking at how we can make it possible for those who wish to do so to express their autonomy in the same way as current donors are encouraged to do by making available a healthy kidney for a fee that is not exploitative.
The proposal has sparked a lot of British press coverage, e.g. here, and here, and here, and here. In each of the articles, the other reported comments are all negative. (I can't tell if British reporters work differently than American reporters and only solicited negative views to balance the proposal being reported as the main story, or if it is harder to find pro as well as con views in the UK.)
Here are links to my previous blog posts on compensation for donors, and to my two papers that lead to unexpected calls on this subject from radio journalists in far places.