Basically you can charge back for the percentage of delays experienced in your travel
You pay £4000 then trains are late a third of the time then you claim £1333 back. Simples...http://www.moneysavingexpert.com/news/travel/2017/01/credit-card-company-decision-to-refund-southern-passenger-could-open-floodgates-for-delay-claims
"Long-suffering Southern Rail season ticket holders may be able to claw back £1,000s if other credit card companies follow the example set by American Express in refunding a passenger who'd been plagued by delays.
Annual season ticket holder 'Sean', who asked not to give his real name, told MoneySavingExpert.com he'd used our "handy guide" to take advantage of protection offered in Section 75 of the Consumer Credit Act and get a £2,400 refund from his credit card provider on the cost of his Southern season ticket.
Section 75 rules mean that credit card companies are jointly liable along with retailers for making sure that customers receive the goods or services they paid for. As a result, Sean's credit card firm American Express (Amex) agreed to issue him with a partial refund of his ticket based on the regular delays he'd suffered."