yep, thats the answer I got. Its actually network rails fault - they don't know when the engineering works will actually take place and so are unable to sell tickets at the mo.
Yep - the work is going on around Berwick. The BHAlbas were quoted prices on train travel between Edinburgh and Sunderland, but then informed that a bus would run part of the journey - fine, you might think, except that that 'part' of the journey would be between Edinburgh and Newcastle. That means that all but about ten minutes of the journey would be by bus.