John Carr married Sophia Easdon in 1825, not Joseph.
I think Joseph is more likely the one who married Ann Cannon in 1830.
There is something a bit off about that marriage in London. Two people from HW going off to marry in London by licence within days of Ann (Cannon) Carr dying. Marriage record said both were single originally, then Sarah changed to widow when she gave the name of John Turner for her father.
Possible Turner connection: In 1851, Sarah's mother Amelia is lodging with elderly widow Sarah Turner. In 1841 Sarah has a possible husband John Turner. John and Sarah Turner had a son also John baptised in 1795 - similar age to Amelia - is that Sara Mullett / Wheeler / Carr's father