So the 101 does seem to relate to 101 years after the Aero was made in 1920. Perhaps this will be named the 'Aero'.
Quote from: https://www.morgan-motor.com/announcement/aero/ Another special Morgan, inspired by Capt. Albert Ball’s specially bodied Grand Prix car, was introduced in 1920. This was called the Aero in recognition of the famous aviator.
Ingenious, but that doesn't explain the "P". The answer is a bit more recent
