Carole, no idea what is going on between the Thurston and Spa(u)lding names but something is certainly afoot

I agree with you that they are likely to be the same family of Spaldings that we had in the earlier censuses.
If you take the Thurston family 1841 census entry you found, John and Mary with children including a William in Gorleston, and then compare against the batch code on IGI for Gorleston (C104831), it seems to bring up some of the Thurston children except under Spalding!
1. MARY ANN SPALDINGChristening: 10 AUG 1833 Gorleston With Southtown
2. ELEANOR SPALDING Christening: 22 NOV 1834 Gorleston With Southtown
3. JOHN SPALDING Christening: 25 MAY 1837 Gorleston With Southtown
Monica