Que posts about the rules of travelling using advance tickets...
Starting perhaps with:
If delays occur while travelling, you will be allowed to take the next available train(s) to complete your journey.
If your first train is cancelled, there is no delay, and it is not clear whether it is "while travelling". If you are not early enough to get a previous one, it becomes a delay with no other option except not travelling.
Then again, if "delay" means ETA later than your booking - and if you think long enough about it you might well conclude it does - that cancelled train
is a delay. Then, of course, if you are there early the previous train is the next available one, isn't it?
There's also this:
If the train you purchased a ticket for is cancelled or is delayed and you still decide to travel, special arrangements will be made to accommodate you on another train (although a seat cannot be guaranteed).
All of which helps very little, unless you want to have a jumping-up-and-down-and-shouting argument and are looking for ammunition.