heater control problems.help!!!

hey folks just got my new car an 01 td5 disco and im well chuffed with it. but i was out in it tonight when i tried to demist the window and relised it was blowing cold air with the panel showing 28 degrees. i played about with the buttons a bit and it worked for a few minutes then lost it again. any ideas?

Was the driver and passenger temperatures set to different readings? - IIRC it will only provide a difference of 5 degrees between passenger and driver so, if one was set at 'LO' and the other on 'HI' you might have a problem

No both sides were set at the same. One minute it was working and the next minute it was freezing.

Water level low ? in my car (not my LR) if water level is low the heater will blow hot while driving but if you sat in traffic and engine is on tick over the heaters will start to cool down and blow cold cause not enough water in the system to circulate at tick over.