But if attention isn't drawn to important terms that would have had a material effect on the decision to enter into the contract it might cause enforceability problems.
If a particularly onerous clause is not highlighted before purchase then it is not binding. All of us who did the first year of a law degree will remember
Shoe Lane Parking which dealt with all of this.
On a customer service level, I think Trainline leave a lot to be desired. They gloss over the pitfalls to try and fit into their marketing spiel of simplicity. Alas, sometimes the herd go in the easy direction and it's not always a bad thing to follow them.
Also on a customer service level I quite agree that it is unfortunate that Merseyrail have chosen not to allow ToD collection at their stations.
But customer service doesn't affect the contract.
I would consider it relatively self-explanatory that you need a ticket to travel, and that if you do not have the ticket (for whatever reason) you need to buy a new ticket or otherwise obtain permission to travel. Permission was not granted. Therefore a new ticket was required to get to a location where the OP could obtain his ticket.
But these are merely opinions expressed anonymously on a internet forum. Seek advice from a local solicitor if you want a professional view as to whether or not the sorts of arguments you present might have merit in a real court if argued well.
Indeed. I am not a professional. If the OP does not agree with me, they are free to do as they wish.
My anonymous internet opinion is that the OP has cost themselves £70 because they didn't want to pay a fiver. My anonymous opinion is also that if they continue to pursue this then these costs will increase. My opinion would be cough up and complain. It would have been much easier to do that when the cost was a fiver. They're free to ignore this opinion if they believe differently. I hope they have a nice holiday.