The Wellcome Trust has actively funded work related to circadian rhythms in past, and their interest in mental health, and broader "discovery research" means your chronobiology research could be funded through one of their many funding opportunities.
Recurring opportunities include the early career award, career development award, and discovery awards, among others.
Accelerator awards, intended for researchers of black, Bangladeshi and Pakistani heritage in the UK, will run until 2028.
A one-off opportunity that may be relevant to chronobiology researchers asks researchers to look at the mechanisms relating heat and mental health. This opportunity has a scope check deadline on the 18th of December 2024 and a final deadline on 21st of January of 2025.