I think the justification is ok... if you want to use the ADC in 8-bit mode then you want it to be left-justified (ADFM=0)
and just read the ADRESH register, disgarding the lower bits in ADRESL.

I think the problem is in the section that averages the readings
Code:
'	Quanticise, discarding top and bottom FOUR elements
'	----------------------------------------------------
	DataW = 0
	For CounterA = 4 to 11
		DataW = DataW+RawData(CounterA)
	Next CounterA
	
    ADCInVal = DataW>>3			' Divide Result by EIGHT
Here DataW must be a WORD since you're adding 8 byte values together which could give you 8 x 255 = 2040.