I use Amex for international too (too lazy). I get the maths why I shouldn’t but I value insurance, benefits and points. Coutts points kind of worthless.

As noted above in my post you want to probably show >£300k annual income and they probably ask for proof. So if earn £50k but charge £500k through expenses you won’t pass the credit check necessarily. Amex wants to know you can cover their high credit lines when push comes to shove.