£20 back when you spend £200 at Costco UK

American Express and Costco are running a targeted promotion for some Platinum cardmembers.  You should be able to see this in the section on the right in you account home page under “your offers”. 
It’s valid until Feb and you get £20 back when you spend £200 at Costco.  I know I would have done it anyway, so it’s a nice discount.