Barnard it appears that your ancestor was part of the Cambridge group of Covills.
Have found Thomas Covill born c1831 in Horningsea, Cambridge, England.
Son of John Covill and Ann Burling. On 3rd January 1850 married Sarah Cornwell at Bottisham, Cambridgeshire. 1851 England Census shows Thomas and Sarah living in Horningsea.
No record on subsequent census - went to Canada?

Regards

Bob