The NICE page linked here collates the current clinical knowledge around fatigue and highlights the current best practice around diagnosis, primary care management and treatments relevant to this.
NICE guidelines are key guidelines for management of specific conditions using the highest quality evidence.
Headway
Headway is a widely known UK brain injury charity.
Headway provide information to patients, professionals, family, the justice system... pretty much everyone.
Headway carry out their own research, put on webinars to help professionals develop their skills and knowledge and support patients and their families throughout their brain injury journey.
There is a wide range of resources related to fatigue.