Skoda octavia vrs 2013 water noise !

Hi there i am not sure if this is the right forum or not but im looking for help or advice in regards to my skoda i have just recently got.

Iv been hit with the dreaded exploding silica bag which has taken a garage 2 months to put right which i think its ok now though i am still hit with another issue that the gsrage says there is nothing wrong with the car.

When i start the car up i can hear water sloshing noise behind my dash board and when i turn the car off i could hear it for five mins then it would stop is this the pump making the water noise ?

But my concern is i can now also hear water sloshing when the car is running and i stop st traffic lights ect .. theres no leaks from header tank or any pipes related , header tank is new heater matrix and radiator have both been flushed for 10 hours so what is this strange water noise ?

The car drives fine no issues no over heating temp gausge works never passes 90 no loss of power or any warning lights just a strange noise i can seem to find an answer for can any body help me or tell me if they have had this issue with skoda.

I have always had vw 's and never encountered anything like this but this is the first car iv ever heard it on have they just cut corners on sound proving ? 

Thanks any help really appreciated