Not quite what I wanted, but you did in fact expose to me that the textField could be populated with something entirely different to the custom renderer.
Basically, I wanted to be able to achieve this: -
This does achieve what I want, but I feel that it's wrong in 2 areas.
Firstly, I feel that just because I know that internally the textField will end up as the target.value in the change event isn't right... This is missleading considering that it's on a prop called 'value' and I would always assume that by specifying a 'textField' prop, then that would always be UI/display purpose data..?
Secondly, the way I have grabbed the dataItem out as a variable in the change event isn't very clean, I feel that this should be something that occurs on the control internally and that the 'selectedItem.dataItem' should be exposed on e.target along side the value prop?
I'll stick with this solution for now as it works, but feels inefficient having to filter the data to get the underlying selected dataItem...