Land Rover Repair: Noise when turned off, air suspension compressor I think, second gap, discovery 2

Question
2004 Discovery 2 TD5 ES Premium - This is an intermittent noise, that happens about 30seconds after it has been turned off and its a kind of buzzing noise & then a clunk. This can happen once only or there can be a 30 second gap and it can happen again. Its not coming from the engine, its underneath the car, passenger side I think.

Answer
It does sound like the air compressor.  The clunk could be a worn out compressor or compressor mounts.  The compressor will run for up to 1.5 hours after the vehicle is turned off.  If yours is worn, you will hear it as it is activated while the vehicle settles.  I would say it sounds like your compressor is on its last legs.   The suspension and valve body are sold as one unit.  They are not too expensive.