Norwich has the best nightlife in Norfolk. "Aha" I here you say, "that's not saying much!" You'd be wrong. The people are relaxed and friendly. The town is not overrun with stag parties (so stags who do go tend to be more welcome than in other towns). And, because of the large student population, there is a lively nightlife.
There are also good activities to keep you busy during the day, with quad biking, kart racing and paintball to the forefront.