Use yer GPS and drive in a series of loops, say one down to Wyn'dom, go one way out and another back, keeping off the "main" roads.
Or head for the North & Mid-Norfolk Railways. Also, the Bure Valley is good, if you like 15" lines. (Not sure if the Middy is open, the other two are).
Last trip down there, we had a drive as Church spotting day out - even some little hamlets have massive churches, all to do with the wool trade.
Oh yes, some of the churches in Norfolk are magnificent. There are a few which have pre-Reformation features as well, since they were sufficiently remote that no-one bothered to come and rip them down. My brother got married in Barton Turf church, which still has its rood screen, albeit with the faces of the most Catholic orders of angels gouged out:
Since you mention Wymondham, it's a pretty town but I don't think I'd go out of my way to visit. There's a good little museum there and the abbey is impressive, and of course it's at one end of the Mid-Norfolk Railway, but that's about all.