Would I use an ellipsis or a comma for ‘Go on... have a listen.’ or ‘Go on, have a listen.’? I guess the true sentence would be ‘Go on and have a listen.’; would you say that’s correct? Thank you in advance and if someone could give a reason why whichever one is correct, it would be much appreciated.
Both are correct, though which one is most appropriate is dependent on the context. Is the person saying that phrase hesitating after "Go on"? If so, then an ellipsis may convey that hesitation better than a comma. If the person is not hesitating, then a comma should be fine.
"Go on and have a listen." seems a bit more informal than the other options, in my opinion, but maybe that's just me.
The rules of punctuation that surround ellipses are kinda weird, but what you have is definitely not an erroneous error. Some people prefer to omit the space after the ellipsis. Others like to leave the space and capitalize the next word. Whatever works for the tone you are trying to convey.
In addition, "Go on: have a listen" is also another way of punctuating that sentence.