Any ideas for this noise please

Any ideas why the engine then goes as quiet as a running engine can be after a couple of minutes?

 

Clicking changes with revs

Engine after two minutes and then ten minutes

 

The noise sounds like from where you are filming is on the front of the engine. I would start by releasing the tension on the serpentine belt with the engine cold and check each of the pulleys. The symptoms you are giving would indicate a bad bearing that quiets as it warms up. Most likely either the tension bearing or the idler bearing. It doesn't sound like an internal engine noise.
Just a stab but a good place to start. The bearing will feel very gritty cold if it is going bad. You may also feel side play. All of the pulley bearings should rotate smoothly. Check all of the pulleys that run on the belt.

 

To my bad ears (been in tooo many bands) the " tick,tick,tick,tick" sounds like to much lifter / valve clearance. It goes away when warm as all of the parts expand and take up the slack.

Get a long screw driver and place the metal end around the motor as you hold the plastic part to your ear. You will hear all kinds of sounds. Your motor was made in Cleveland, so I call it the "Cleveland Orchestra" : ) With some practice you will know the sounds that are normal. This works well to locate pump bearings going bad too.

Good luck.