Last year I travelled BKK-LHR-ZRH in CW/CE. The onward to ZRH got cancelled (as did some other late EU flights). I stayed in LHR overnight and got rebooked the next day early evening. I then tried to check in my bags for the second leg in the am hours but was told that it’s not possible until midday due to yesterday’s backlog or what not. The agent was very professional though and suggested to wait in the arrivals lounge until like noon and then come back and check in my bag.
You’re travelling first and I don’t know if F passengers are usually excepted should this be a common rule during/after flight disruptions. Anyway safe travels and enjoy FIRST!