Hi Painterlady
There are 6 Mitchell Stones in Horsham, St Mary, but unfortunately I dont think that any match your criteria; although possibly No 449 looks promising.
No 183: MITCHELL Lucy, Wife of John and Daughter of Hugh & Elizabeth Orlton
No 447: MITCHELL Edward, son of Samuel and Phoebe, 1822
No 448: MITCHELL Samuel, son of above, 1833
No 449: MITCHELL Harriett, wife of Isaac, 4th August 1850 and Daughter Ann, 1857
No 919: MITCHELL John, son of Edward and Catherine, 1813 or 1815, aged 66
No 1146: MITCHELL Matthew, 2nd November 1880, aged 65 years
Hope the above may help your research
Chris in 1066