Sorry, Looks like "the jig is up" at least for USA reservations. I just tried reserving at 7 different hotels that show the "TESCO COUPON" and NONE of them even has a place to enter the code any longer. I did get my first one to work a few days ago and AS OF NOW the reservation is still good but I think the fun is over.
Have you tried the 200 - 400 values? They are still working.
The problem isn't the VALUE the problem is there is no longer an "ENTER TESCO CODE" option on multiple hotels in the US I tried despite the "check mark" on the hotel saying the code was accepted at that hotel.. Never got to even enter the code. It might be a US issue, no idea.