FWIW, in your Tilshead - Bristol route, I would reroute from South Wraxall - head up towards Monkton Farleigh and then strike north east on Link Lane. That drag out of South Wraxall is one of the most surprisingly unpleasant bits of road in the area. It's a short diversion but it's overwhelmingly nicer, a smoother gradient and much less grim.
If you want a nice B&B, or just a good farm shop for a stop en-route, The Three Daggers is on the B3098, just before Bratton. They've got their own brewery, and lovely cakes.
FWIW, in your Tilshead - Bristol route, I would reroute from South Wraxall - head up towards Monkton Farleigh and then strike north east on Link Lane. That drag out of South Wraxall is one of the most surprisingly unpleasant bits of road in the area. It's a short diversion but it's overwhelmingly nicer, a smoother gradient and much less grim.