I'm trying to book a single London to Newcastle on 28 May. Despite there being advance tickets available for the 09.30, 10.30 and 11.30am trains when I go to seating preferences I get an error message saying there are no seats left. I don't get how there can be advance fares available but no seats. And are so many trains really full almost two weeks out?! I've been in touch with LNER via twitter who have just said there is no availability.