Ok, thanks. I won't have a chance to look at it again until Monday but I bought 3 of these and all are the same so unlikely an issue with the sensors unless it is a faulty batch.
The Wiki page for this that is linked in the post has 1023 an 11 as the values from the digital output.
I suspect this is not the correct thing for the application in mind but as I have them I am still interested in getting them to work for some potential future use.