I'm assuming you got into CS1004 fine? Like I said a pre-requisite to a same year module has to take resits into account.
I wouldn't worry too much about some of the posts that have been made regarding how you will now have to think about changing your degree, if computing is even your degree subject. I know from experience that only you yourself can know what you are capable of and marks first time around can be no good indication of what you are really capable of.
I certainly found CS1002 to get easier the more I did, same with second year stuff, it's just down to the individual really.
By the way, if you are having trouble getting them to accept your claim of exceptional circumstances, a trip to Dave Roberts may be in order