Hunch. The order that moved the deadline gives only a new cabinet as the reason and names no plan, and the last time that happened, in 2024, no plan came.
The plan market resolves on gov.uk: YES if by the end of 17 December 2026 the government lays its reply to the Climate Change Committee's 2026 report and publishes a new government-wide plan for meeting its carbon budgets on the same day, and NO if there is no reply by then or the reply comes without such a plan, with a plan for one sector such as power or heating not counting. BBC News and the Guardian settle it if gov.uk cannot be read.
We looked for cases where a UK government used its power under the Climate Change Act to move the deadline for its reply to the climate watchdog. We found four such orders, one a year from 2022 to 2025, and none before 2022. Each time the reply came before the new deadline, between zero and five days early. Two of the four times, a new national climate plan came out on the same day. (legislation.gov.uk)