The bright fireball recorded off northern France at 02:59:20 this morning was the cause of these flashes. The object that caused the fireball has now been officially named 2023 CX1:
https://minorplanetcenter.net/mpec/K23/K23CA3.html
It is the seventh time that an object has been discovered just prior to entry. The previous ones being 2008 TC3, 2014 AA, 2018 LA, 2019 MO, 2022 EB5 and 2022 WJ1.
Unfortunately weather over most of the UK was poor but people along the south coast saw it.
https://fireball.imo.net/members/imo_view/event/2023/937
John Mason saw it from Sussex and has sent me a video. I saw the flashes through thick cloud from Chelmsford at 02:59:21.