Planning this trip was made possible by using websites as Trip Advisor and Lonely planet thorntree(have to register to post questions but can view existing posts).
Best guide book I feel is the Bradt Guide to Ethiopia, edited by P. Biggs (5th Edition), ther website has an updated section on several countries includes Ethiopia.
As this trip includes 3 internal flights in Ethiopia with Ethiopian Airlines I joined their frequent flyer
programme , Sheeba miles, free membership and potentially able to check in free excess baggage.

Flying BMI, Aberdeen -London Heathrow-Addis Ababa but due to their winter timetable flying back with Ethiopian Airlines ,Addis Ababa-Rome-London-Aberdeen.