The UK rail online solution is currently being enhanced!
Some travellers may have experienced a new design for one-way bookings since few weeks. On top of this, a new feature is available starting 5th of July that allows you to cancel a booking direcly from the website in a very easy and fast way.
Once your rail booking has been made, get to the the trips part to view your itinerary: a cancel button will be displayed if the feature is available for this booking. During the upcoming month, this option will be available more broadly.