Hello again,
The Wills database on the Cheshire Record Office site has an item for a Will of a Reverend Ferdinando Casson, Chester, dated 1838. It is such an unusual name I wonder if there is a connection to your Rev Casson?
The 1822/3 Directory, which is online, shows the Rev M Casson to be at The Commercial School, Barrs, Foregate St. This is also on the Cheshire RO site.
There is an entry for Rev Mr Winfield in 1789, he is at The Academical Boarding School, Northgate St then too.
I am sure that there would be something for these two establishments in either the RO, or the Chester History and Heritage Centre.
Jo