ADC not referencing to 4x fixed voltage referenced - PIC16F18854
I have found a solution to the above.

In my code, I had selected the channel, waited for the acquisition time (from the datasheet), then started the conversion using the function named "ADCC_StartConversion" generated by MPCC, which accepts the argument for a channel. 

This function then re-selected the ADC channel and flags the ADC to begin "ADGO". 

Despite the datasheet stating the requirement for an acquisition time, Microchip have implemented by MPCC, a function that will never work as designed.

Really, there should be an "ADC_SelectChannel" function and then an "ADC_StartConversion" so that the user can generate their own delay, or for the function to include the stated delay.