If I was reviewing a refund request for a ticket bought through the forum's site or TrainSplit, I would certainly agree and provide a full refund under this condition.
Good on you, another good reason to use the forums site to book tickets. Out of interest, having taken the decision to refund are third party retailers guaranteed to get the money back from whoever it is in the railway they do business with, or could that lead to a dispute between the site and the railway?