Norton Anthology of English Literature Vol I and II.
However, I would avoid buying them yet (unless you can find them cheaply) as reading lists are subject to change at the whim of the All Powerful Fuhrer-in-Chief, Dr Archibald (Head of Department don't ya know). Though I would put money on them being on it, there might be certian editions they want you to get which differ from my years (again, though, I doubt)
Basically I'm covering my back so you don't buy them then shout at me when they're not there.
Once more, I reiterate that the 'very short intro' to literary theory is worth a buy. You can probably get the other grammar/theory books off 2nd and 3rd years. In fact, the grammar books are only really needed if you feel you don't know enough of it well enough. Yes, you WILL lose marks for mistakes like its/it's, effect/affect, and (one that caught me out) semi-colons with no following complete sentance.
Not surprisingly, when doing an English degree, your fellow non-English friends will ALWAYS turn to you when they have a problem with phrasing/spelling/grammar. Be prepared to be perfectly able to explain, with easy to follow puppet movements, what a verb is to a confused maths student, and to explain to historians quite WHY you can't use comma splices, no matter how pretty they look (Yes, I've had to do these both this year).
(*cough* do Old English *cough*)