Not sure if you noticed the marriage in 1813 for a Daniel Boys (bride Elizabeth Cory)?
In the 1841 census for MKV, Rebecca Leach and Daniel Boys were aged 60 (rounded ages), as was an Ann Boys (a single occupant but maybe a widow) but there are no Boys in the 1851 census.
Checking the PR, parents John and Mary Boys baptised Elizabeth (1772), William (1775), Susannah (1777), David (1781) and Mary (1786) and Rachel and Richard (1788). These are also transcribed as Boyce.
Hope this helps...