I pay for an annual oyster card, initially i was receiving the emails saying i was being refunded for my delayed journeys but seeing no refund. It was when i went to renew my Oyster card for the year a few weeks ago i was automatically discounted the accumulated delayed journeys which was great and did make a difference- nearly £50 when i only signed up a few months ago. Once you have signed up the website is super helpful and automatically lets you know a few days later you will be receiving a refund for a delayed journey, and as i live on the district line this is quote frequent! Really glad i found this website and looking forward to another discount next year when i renew my oyster!