Thanks Chad, all good, this problem was a blessing in disguise as it forced me to address the usability of my set up from a business point of view and to remember the KISS principle - Keep It Simple Stupid.
The flexibility of these forms also means there is always a way round everything!
With your help on hiding from roles - I assume though that hiding from registered users (technically a role) still does process the field? (I can test this after I've had my morning coffee).
I was a bit baffled as to what would be the point of having a field hidden from a role but not saved to the database but I am guessing this is still a useful feature when you simply want to gather information via a dynamic email.
Thanks for the bug fix, Jess