Bobo, thanks for taking time.
The D800 was one option in mind. The other is a D600 for landscaping and general photography and a D7100 for birding.
I'm led to believe that since I bought the D200 (an excellent camera in my view) back in 2007/8 the technology and resolution have improved so much that noise is less intrusive. The D7100 has a high enough resolution plus the double in camera crop of newer DX bodies to allow post cropping to fill the frame without a tc. Ideally though I'd like to be sat on the same branch as the bird
so need to practice stalking skills.
The D600 would allow me to develop my landscaping in glorious full frame quality which I believe is a revelation to someone like me with only DX experience.
The cost of both cameras would be roughly in line with D800E or so I keep telling my wife! Not sure the newer D610 is worth the extra cash they ask.
Thanks again and I'll try not to bore you too much whilst I learn.
Cheers
Ned