Cheese & pickle & lettuce sandwiches.
A big piece of chocolate stout cake.
I almost always take something in, I've been privy to the joys of Nottingham University catering in the past, and I avoid it whenever possible, really expensive (like £5 for a decent meal), of dubious quality. The only reason they can do it is because we're a campus university, so you have to walk a mile to the nearest other sandwich shop.
When I was working at University of Canterbury, New Zealand, the catering was all organised by the student union. They made enough profit on it (plus the rents for the bookshop etc.) to pay for union activities, and still managed to have good quality, tasty food that was freshly cooked and dirt cheap. Whereas here we pay a fortune to useless contract caterers for terrible food.
Joe