Its not a silly post, as im sure its a familiar position to many, many people. You have just been sensible in addressing it now rather than pretending it will go away - if you have profound doubts, tis best to address them before you go. As ive said on previous posts, choosing to go somewhere for 3 years is a big commitment and you should be sure about it before you go. However, is this a recent feeling or a long held one?
I know that on results day, when I got them in the dim and distant past, I remember having butterflies that this seemingly distant and wonderous place that seemed an age away was now all but here. I think this kind of feeling, and understandable nerves about going somewhere and doing something new, fitting in are to be expected. If, however you have had it for longer, its probably worth giving it some further serious thought.
Rest on your feelings for the weekend and if u still feel the same by monday, then take some action. Either way, I would certainly suggest talking to people at college about how you feel as you need to know that, whatever decision you take, you did so for the right reasons and with all the relevant factors taken into consideration.
I wouldnt be too scared about one year out becoming many. If you want to follow your chosen path enough, then you will return to it. Plus, you have plenty of time on your side too! Some more life experience isn't going to do you any harm, especially for something like journalism where (I imagine) you need to have been around a bit to succeed.
Give yourself a bit of space, and then see how you feel as ive said. let us know how you are feeling on Monday, and take it from there would be my personal for the time being.