Totally unconnected as far as i can see Ellie, it sounds like a very noisy volume control pot to me. Quick method of basic cleaning is (with the radio off) turn the volume up and down quickly several times, all the way in each direction. Granted you need to be a bit of a contortionist to manage this but it's possible - just!
If you are able to remove the radio and locate the volum control pot, squirt some contact cleaner into it and repeat the up/down quickly several times. Should cure it.
