I just found Thomas Cator on ancestry in the Cambridge University Alumni and it says he was born 19 Feb 1790, son of Joseph, gent, of Beckenham, Kent, and Diana... married Lady Louisa Frances Lumley, dau of John, Earl of Scarborough...
Thomas Cator
So Celia's 2xg-grandfather Thomas Cator definitely ties up with my tree. Will have to figure out exactly how we are related tomorrow though!