Thanks for the response chaps
The above listed books were good but I am looking to supplement this info.
I am a maintenance engineer currently studying for further licences, and as such my requirement is for books detailing the fundamentals of automatic flight control systems, representative working systems and system interfaces.
Texts also dealing with how the systems are actually used would also be benificial, but as Shawn has pointed out, these do seem to be few and far between.
Purchasing these type of books is a tad hit and mis as inevitably if you buy on line you do not get to flick through it first. They are also erring on the expensive side. I guess knowledge does'nt come cheap these days.
GR