Hello Rongrose - I'm going back into my dim and distant memory here...bear with me...
I had a look at the census pages and one of the next addresses is Small Bar Dick, I'm fairly certain this is now Small Beer Dike Farm or something similar. I also looked at the description for the enumerators walk and Batts is mentioned as is Heath Mill and also Nutbourne Mill...so we can discount Nutbourne Mill.
I looked at the Sussex Mills website and I know for certain that at least one Watermill that I know of is not on that website soooo....going back to memory I am sure there was an old, small watermill somewhere up near the end of Batts Lane.
We used to walk through Pulborough, up Batts Lane and across the fields to the Rising Sun Pub at Nutbourne. The mill workings had gone but the house was still there, also from memory I think there was a small stream that ran alongside.
Look at Google Maps, put in Pulborough and get the larger image up.
you will see Pulborough and Nutbourne - in-between there is a small road, triangular shaped, click on that twice and you will see Batts Lane and Nutbourne - the sat. image is interesting too.
You might try and contact the Sussex Mills Group, they may have a someone who could investigate.
Hope this helps
Suey