I have just uploaded copies of the first printing of Chatterton's two letters to James Dodsley, the Bookseller and Publisher. It was Chatterton's first attempt to secure a Patron - before he moved on to Walpole.
The images were taken directly from my own copy of Britton's book about Redcliffe Church (1813), which also contains a section on Chatterton.
John Britton was a very interesting fellow. He was an admirer of Chatterton to an extraordinary degree - which marks him up in my book.
I have added the two images below which show the esteem within which he was held - note the massive gravestone.