A new card reader has been introduced at Iver station by TfL for contactless card payment, although it is not yet enabled for Oyster cards. However, fare capping is yet to be introduced (expected Spring 2020) which means you will be charged for a single fare each time you use your contactless payment card, therefore, it may be more economic to purchase a return ticket or London travelcard.
If you wish to claim a 'Service Delay Refund' and have used a contactless payment card, you can do this online via your account on the TfL website (link). If you have purchased a paper ticket, currently the only way to claim a refund is to contact TfL customer services, either online or by email (firstname.lastname@example.org), providing a copy of your ticket and receipt, along with details of your delayed journey. (GWR Delay Repay no longer applies as services are now operated by TfL.)