i made a similar choice. i want to be a writer and i got an offer from oxford, was going to get one at warwick for english & creative writing, and already had one from goldsmiths. i went for oxford, and withdrew from warwick.
why? i figured that there's enough creative writing stuff at oxford, especially my college - what college is your offer from? also, i thought that before university i hadn't read much of the canon, and didn't have enough of a grasp of what had already been done. oxford forces you to go through every period and do most canonical writers. you also get to discover more obscure writers to write about though, it's not just the canon, but it's useful, although not massively fun all of the time. i don't find much time to write in term, or not as much as i'd like, but i've written some poems here and more in the vacation, and i workshop them and show them to friends and it's fairly good for creative writing anyway.
i've heard mixed things about creative writing degrees - personally i think reading is probably more useful than workshopping in improving writing at this stage, anyway. the courses are very good for building up contacts in the publishing industry, but perhaps not as good for actually writing as you might hope. most of the people that you hear of as having famously graduated form creative writing programs actually did an MA. currently i'm considering applying for one after doing my first degree at oxford.
but at the end of it, go for what you want to go for. sometimes i really regret not going for english & creative writing at warwick, because the course was just awesome. i don't know much about uea, since i didn't apply to anywhere in east anglia (needed to escape), but if the course is good and it's what you really want then just go for it.