S B.

Following Rentalcars agents advice, I managed to open a case after the contracted rental period was completed. Case submission is tricky; my advice is to prepare all your supporting attachments ready to attach from your laptop before you start. On the case entry page, you are only given a 350 character field in which to enter your case summary.
Since this is usually insufficient, prepare and attach a separate file with your full account of what happened and what you are claiming.

Try to complete the case summary and uploading of attachments promptly otherwise you may have to start again. On case submission, you will see an onscreen confirmation message and email with subject "Looking into your issue". After that, it took several emails on my part to expedite a refund - it took about 6 weeks. Other than the fact that denial of service at the time on a technicality totally disrupted my holiday plans, there was significant extra cost of booking a replacement hire car with another more reasonable supplier than Europcar!