i haven't recieve it too. i just had my cas number last week, the unconditional offer seems 1-2weeks later than that.
but you do not have to worry about, if you book your university accommodation before the deadline(1 July,2010), that is alright, you're gonna have your room. and if your requires of your university accommodation a little strict(quiet, same sex, non-smoking...), your offer will be a bit later than others.