Eric on the NFHS, as you say the name changes there are 8 baptisms for children of Thomas and Elizabeth at Colston Bassett, sadly no William.
The earliest 11-8-1822 Mary Ann dau of Thomas and Elizabeth BURRELL
the last 27-3-1835 Elizabeth dau of Thomas And Elizabeth BRADLEY
3 children baptised under Bradley and 4 under Burrell, one under Burrill.
the marriage same Church
26-11-1821 Thomas Burrell and Elizabeth Gun.
Burial same Church
6-11-1853 Elizabeth Bradley abode Colston Bassett no age given.