Just echo what others have said.
NAS spec V8 autos and 50th aniversary edition defenders are the only autos I know of. Probably need LPG conversion too unless yer first name is 'sheik'
Automatic Discoveries will be a lot more common tho'.
I currently have a Defender, but previously had a 300TDi Auto Disco. Basically you get a lot more toys in the Disco (lecky windows, CD etc) for less cash than a Defender of the same age/mileage. Discos are also a lot more comfortable than the Defender.
However, and this was a big issue for me - the auto box robs a lot of power from the 300TDi engine - having owned a 300TDi Defender I knew what was there, but the disco just could'nt deliver it. It was however fine on the motorway, once up to speed, and I really liked cruise control. But for everyday toing and froing the auto was frustrating, despite being a very easy drive. I've not driven a TD5 auto, so dunno what they're like in comparison.
So, if you want easy driving comfort a disco auto is probably the best bet. Just make sure its got a full service history and a new cambelt (diesel).
For me, I prefer the more basic Defender.
cheers
Intertidal