I managed to get some astrometry of this very small object this evening and it was a bit off track. An updated ephemeris is attached. Tonight it is around 19.7, tomorrow night (Tuesday) it will be 18.6 moving at 5″/min and Wednesday night it will be up to 16th mag but accelerating through 30″/min. It then moves rapidly south and we lose it as it comes within the geostationary satellite belt for a short period around Sept 24.45.
Note the ephemeris is for my location and the position will be different for you. This will become more significant the further from Essex you are and the closer the object gets. Let me know if you want an ephemeris for your location.