Sorry I missed you at the birdfair, Graham. Someone mentioned you'd been around in the optics marquee but I did demo the contax to a few guys who know you quite well.
I took delivery of the Contax external battery pack at the show, seems very well made with a cable that isn't going to suffer from the rough and tumble you get in the field. It's slighlty different in shape to what i expected, being long and slim, so it tends to fit better on your tripod or scope than the dumpy dual force pro for Nikons. It does recharge the internal battery when the camera is switched off and connected to the battery pack. When purchased, it comes supplied with 2350mah nimh batteries and a fan cooled AA charger (fan cooled??!!)
regards,
Andy