Hi OldSteve
First and foremost, thanks for your response. After your prompting I checked the Hi-Low Tech site (yet again) and managed to locate the AREF pin (pin 5) with the help of my wife. 
Making use of the internal 2.56V AREF would be very attractive. I'm using the High-Low Tech Core but I can't see any mention of the internal AREF.
I've tried making contact with MIT Media Lab but I'm not confident I will get a response after reading their FAQ.
I will therefore try your suggestion of running a test as you outlined above. I will keep you posted.
Cheers
Jase