What an amazing website, Mobo!
Rather puts my amateurish efforts to shame. Made me wonder, though, whether your John Whittaker Williamson, b. 1805, might have known my William Dyson b. 1795 - same location, and same sort of occupation, variously "grocer", and "master carter". Mention of all those places of baptisms, marriages, burials. etc. brings it all into sharp relief for me; have only been to the Manchester area once in my life, to watch a Man Utd. v. Spurs game about 13 years ago with my brother, when we stayed in the Trafford Hotel, which I think used to be Trafford Town Hall.
But Salford is an area I shall visit soon to make sense of all this geography...
Keith