OK when (if) you get a response
My parcel was delayed / lost with Royal Mail and as I had a deadline for when I needed the item, I tried to contact Cotopaxi's customer service to request a replacement or a refund so I could shop elsewhere. They offer a live chat and email address.
Unfortunately the live chat is not live, it is just a basic AI with no human behind it, so I saw no response to my messages over several days. While I did hear back on the same day to my initial email to say they would investigate with Royal Mail, come 6 days later I had not heard back. I managed to find a phone number for the company managing their UK operations who put me through to Cotopaxi's customer service - everything from here on was smooth, with pleasant and fast customer service support, who were able to sort a replacement item. However the slow and lack of response through the provided customer service route was concerning given my urgent need for the item.