I've no idea what the refund process would be with Carphone Warehouse or EE if you decided to return due to not being 100% happy with the handset, unable/unwilling to cite a particular fault. However, I certainly have no complaints with Google's customer service and if I do buy another Pixel it will be through the Play store again.
Thanks for the update. I'll head in store this weekend and see what they say r.e returns.