The chassis number can be found on the chassis next to the steering column (RHD cars).
If you look into the engine bay on the drivers side you will see the steering column crossing over the chassis, at this point the chassis number should be on the main chassis leg (see picture below).
There should be a 7 digit number and if the vehicle is an original "Export Model" the number will start with the letter "R" for RHD and "L" for LHD
On the bulkhead there is a brass plate (see picture below) with a Body Number, (this is not the chassis number) this number (if original) will correspond with the last 4 digits of the chassis number.
For example if the chassis number is R6214537 the body number should be 4537.
Below is the Rover chassis number codes for models from 1940 to 1949
Seven-digit numbers, preceded on Export models for 1946-49 by an R or L prefix to denote right hand or left hand drive

Chassis No. location (pic below)

Body No.Plate (pic below)
