2010 octavia rattles

Please help I recently bought a skoda octavia vrs 2010.

When ever the car is reved at 2000rpm there is a weird rattle but can only really be heard from inside the car.

About a week later it went into full blown rattle like two bits of metal grinding on each other but again can only hear from inside of the car. It stopped when the heater was put on to auto then off. But now I can hear a faint whiting noice and am getting very paranoid about it. Never had problems with my last octavia :(