I had a very bad experience. I recommend do not use Trainline if you can preserve your right to receive a reimbursement and to avoid bad surprises! I bought two tickets in Trainline to travel from Paris to Milan in TGV (69 euros each). The train was cancelled and TGV did not validate the change of train with those tickets: the person in charge of the desk attention in the TGV office at Gare Lyon said "sorry sir, but you bought the tickets in Trainline; there is another train to Milan, via Zurich, in 10 minutes and the only thing you can do is to buy new tickets (226 euros each!) here with TGV and ask Trainline for refund your unused tickets"). So the answer I had from TGV was as if the tickets bought in Trainline were fake. I would have avoided the whole problem and the lost of money if I had bought directly from TGV and not trusted Trainline. Trainline reimbursed me 69x2 euros, but I had to bear the difference. 288 euros lost just by choosing Trainline!