@gerrit, I am booking international tickets and can not yet book the UK part, (too far out in date.) But trying for nearer dates I am not able to get the ticket selling sites to accept any 'London international' or London CIV' as a departure station.
That is on the National rail as well as on the railway site of the company that does run the train.
I do not think I will need to buy in advance as I will have about 3 hours between the first of the connecting trains I can get and the first train that is quite a bit more expensive, but it would be great to understand this.
@Willeke I've personally bought my CIV tickets at a staffed station, but that doesn't help if you're coming from abroad. There's some info on seat61.com.
I've only ever bought UK train tickets when living in the UK.
I will keep that in mind for the next time I need tickets in the UK, as this time it is not going to safe me more than a few pounds, and it might not work at all as most trains do not seem to have advance tickets.
