I also had a problem booking with a US credit card at premier inn, and I see this has been going on for at least five years from other posts on this forum. My reservation is in limbo, they may or may not charge me at some point and they may or may not accept my card when I arrive. This is very disturbing.
The problem is not with my credit card, which is a travel card and has been used for other hotels, train tickets, etc.
Has anyone with this problem had an issue upon arrival? Were you able to keep the Saver rate or were you charged a higher rate?