Welcome to the site Joe! A new thread might be appropriate if you're looking for advice, but as a starting point I'm always impressed if a restaurant stocks at least one good example each of a lager, wheat beer, stout and IPA (that's just my preferences though, others might say that you need more than that, and obviously the more choice the better! That's my minimum though).
For lager, I'd look at either Brooklyn Lager, Sam Adams, or Budvar.
For a wheat beer, I'm a big fan of Konig Ludwig Weissbier (and the dunkel version as well).
For stouts, Black Rock Stout is meant to be exceptional, and isn't widely available yet so bonus points if you stock it! Also good are O'Hara's Stout and Porterhouse Plain.
For IPAs, if you can get a Galway Hooker tap installed then you absolutely should (unfortunately, unlike the others mentioned here, it isn't being bottled yet). I'm a big fan of Sierra Nevada Torpedo IPA too.
Oh, and you should probably have at least one or two trappist beers too, if you want to be regarded as having a properly "good" beer list. I have no real preference between the ones widely available, and I don't think any of them are particularly bad either. I'm sure someone else can weigh in on trappists in more detail.
Good luck with the business, hope it goes well! Let us know how you get on with it.
EDIT: Oh, and I guess you'd need some sort of british ale type thing as well, Old Speckled Hen or something maybe?
EDIT 2: And while you're at it, maybe a witbier, and a Bock, and an Oktoberfest Beer of some sort, and a...
EDIT 3: It's not hard to get me going, is it?