I have just come across your postings regarding Jane Wells Webb. It so happens that I have covered some of the same ground while researching the background of John Claudius Loudon. You may be familiar with the book: "Lady with Green Fingers. The Life of Jane Loudon" by Bea Howe (Country Life, 1961) Howe states (page 13): "I have constructed the first years of Jane Loudon's life, when she was a girl living at Kitwell House, from the autobiographical material which is embedded, so discretely, in her books." She also thanks Miles Hadfield (the garden historian) "himself a Jane Loudon fan" for providing local material which he had collected. The book has two photos of Kitwell House, taken when derelict, in 1951, ""demolished to make room for the erection of a vast secondary modern school."
According to Howe, after the death of Jane's mother in 1819, Thomas Webb "took his daughter abroad for a year's travel on the Continent. ... On leaving Southampton, she cut off a lock of her hair and sent it, with some suitable line of verse, to her much-loved cousin, Harriet Swinson. [see below] For a year the Webbs, father and daughter, toured Europe, sight-seeing , and improving Jane's education by the study of German, French and Italian. On their return to Birmingham, Mr. Webb, facing heavy business losses, decided to turn his back on city life and retire to Kitwell House ... outside Bartley Green. He had bought Kitwell House soon after Jane's birth, but it had been let for some years. Now it was empty again." The house contents were sold in late 1824 (Aris's Birmingham Gazette: Monday 25 October 1824: advertisement on page 2; Monday 8 November 1824: advertisement on page 2; Monday 15 November 1824, advertisement on page 2 (repeated Monday 22 November, page 2. These ads give some detail about the property as well as its contents.)
I think it was Howe (page 26) who started the oft-repeated story about Thomas Webb of Birmingham: "Little has been recorded of him except that he was a well-to-do business man living in easy circumstances." Sarah Dewis, in "The Loudons and the Gardening Press" (Ashgate publishing, 2014), refers to him as "a prominent Birmingham businessman and engineer." The ODNB article on Jane Loudon, by Ann B Shteir also mentions Thomas Webb as a businessman- and says that Jane was born at "Ritwell House". As you have found out Thomas was, in fact, a well-to-do attorney!
I have been unable to find anything about Jane's mother, however. Was her name surname Wells, perhaps?
The brief mention by Howe of cousin Harriet Swinson got me onto this site, since there is some relevant info about her. Family search says that she was born 5 September 1831 at Bordesley; her father's name was George Newton Swinson (born 1789) and her mother's name was Mary Ann Swinson. George Newton Swinson was a surgeon [who confusingly also had a son (thus a brother of Harriet ) of the same name- this younger George Newton Swinson was born April 1833 as Bordesley, later moving to Ashwell and finally Australia.] The possible Jane Webb connection is that the older George Newton Swinson's father (called simply George Swinson) had a wife called Mary Webb. Was she related to Thomas? [England, Warwickshire Parish Registers: Marriage. George Swinson, age 24, residence St Martin and Mary Webb, age 21, residence Northfield. 10 January 1788. Marriage place Worcester.] So far I have not been able to tie Mary Webb to Thomas Webb.