I read it as:
as shown on the itinerary ([presented by the journey planner on
www.nationalrail.co.uk] OR [from a Licensed Retailer]) AND ([in connection with the purchase of a Ticket] AND/OR [including the relevant restrictions applying to that Ticket]).
So you need to be using the itinerary presented by the journey planner on
www.nationalrail.co.uk or from a licensed retailer, and that use must either be in connection with the purchase of a ticket and/or including the restrictions applying to the ticket.
This would seem to fit the bill with consumer law as well, because it's saying that the itinerary used in connection with the purchase of the ticket is valid even without taking into account the restrictions applying to the ticket (which the journey planner should do), but if your use of the journey planner is not in connection with the purchase of a ticket the journey planner must include the relevant restrictions applying to that ticket.
Does that make sense?