I would like to buy an off-peak return from London to Ledbury. My preferred route is via Birmingham, which seems to be a permitted alternative route to the GWR service during the closure of Nuneham viaduct. But how do I buy a ticket for the direct route - I think the restriction is 'via Evesham'? If I go to the journey planner there are no journeys offered via Oxford and the Birmingham route is more expensive than usual.