To try to be a bit more helpful.
What various legislation does the CAA derive authority and guidance from?
I think it's the Civil Aviation Act that gives it powers and the Air Navigation Order and a few other bits that support how it discharges its responsibilities. CAP393 contains the important bits.
The functions charged to the CAA by the legislation?
Civil Aviation Act and directions from the Government - see the back of the CAA's Annual Report.
The Core Operational Divisions and Departments of the CAA Safety Regulation Group?
Heaven knows.
The Role of the CAA in the work of the JAA and EASA?
As above.