In a Gazelle at night with a new "pilot" showing him the ropes on NVG and experimenting with the new unstabilised thermal camera. Suddenly fly into a cb and snow, unforecast as the best ones always are, at about 1500 feet in hilly country! Not enough fuel for an IFR recovery not that I considered that for too long with the turbulance and icing potential. The pilot reverted to instruments (he was Amber rated with about 20 hours experiance). I turned him on to a DR heading for a valley and started to descend, at 1000 feet the glow of a village appeared in the NVG but nothing to the naked eye. The village was identified in the TI so I trimmed the camera to the center of the village and set it at 3 degrees down and started to talk the pilot down. At about 500 feet a known landing point was identified on the TI, still litle more than a glow on the NVG, so I continued the talk down. At about 200 feet the landing site lights were visible on the NVG so I took control and landed. After shut down we clambered out to be met by the residents of the site who wondered what we were doing as we were not expected!! We were also standing in 2 inches of snow that had fallen in about 10 mins. After shaking hands, thats shaking hands whilst shaking, we discussed what we had done in rather high pitch voices and went to find a bar. Damn thing was shut, well it was 1 o clock in the morning, so we found a video and pressed play. The vid was Black Adder "Private Plane", just what we needed. . .. .If you are out there Nick, I hope you remember how much we both learnt that night. Good luck.