Please check your route/vehicle yourself on the tfl ulez website.  The website says that there should be plenty of warning signs showing that you are entering the ULEZ.

The following is only intended to be helpful to our customers whose vehicles do not meet the ULEZ requirements.

I have looked at the map and the nursery is not in the expanded ULEZ area that will become effective on 29 August 2023.  The nursery is inside the M25 but Chequers Road, Noak Hill Road and Church Road are outside the ULEZ.  The M25 is not included, nor is the A12 on the Essex side where it meets the M25.