Just a tip here, please don’t use Trainline to buy national rail tickets due to their fees.
It seems that unless you are buying a walk up ticket for that day and paying using a debit card you will be charged a fee.
Which means all advance tickets are more expensive through trainline.
Use a train operating company site instead such as Southeastern or Avanti and buy the exact same tickets for the price that is stated on the national rail fares site with no hidden charges!