I have tried at 2 stations to reserve a seat in 1st class on the XC 09:15 Southampton to Reading on 10th July only to be told by one station that it could not be done, but they told me that about 2 others which the other station managed without problems. The second station told me "there are no complimentary seats available" but could not explain what this meant - is the train full? It is marked as 1st class and reservable in the timetable.