One thing about customer feedback and in general listening to your customers, is that it only tells you what your current customers think, and usually only a vocal minority of them. To expand the service you need to reach potential customers as well.
I suspect it'll never be released for commercial reasons, but I would love to see a sample dataset of queries that people make online with National Rail Enquiries. Where do people actually want to go? What journeys do they want to make, and how well does the current rail network (and timetable, and fare system) respond to their needs?
To take an example from another thread, would it show lots of people looking for a late-night train from Stratford to London? Are there flows that could justify a new direct service (I've always wondered about Evesham/Pershore direct to Birmingham)? How about journeys where people look up the prices, but a smaller proportion than usual click through to purchase, perhaps because the fare is too exorbitant?
You'd have to treat it with the appropriate degree of caution, because a lot (maybe most) of
NRE‡ users are looking for journeys they already know they can make, but it would be fascinating and perhaps very useful data.