I'd look to try to stretch it by 1 day if at all possible. If you just don't have the vacation time banked, and you aren't subject to blackout dates, maybe you can stretch it if your company gives you off any holiday weekend - like Columbus Day, Thanksgiving, President's Day or MLK Day.
There's definitely ways to stretch your funds - look at something like Couchsurfing.com to see if you can find a free place to stay, check into convent and monastery lodging (very basic rooms, but clean and many include breakfast), consider hostel dorm rooms. You can eat cheaply - if your lodging includes a full Irish breakfast, then take advantage of it and you can skip lunch on a breakfast that big. Otherwise, eating a bigger meal at lunch and a small dinner is cheaper. Consider things like daily specials in a pub, or get takeaway from places like Marks & Spencer's or fast food places.
And if you absolutely can only spend 2 days there, then just rally and push through. I've done a few of these from the East Coast to various points in Europe and sometimes just a quick 1 to 2 hour nap before dinner makes me perk right up so I can go have a late dinner and then hit some pubs or bars for a few hours.