I've found hotels in Europe can be very strict about room reservations/capacity. A couple of times when travelling solo in Italy, after I've made my reservation for ONE or a Singlw, I've received e mails from the particular hotels warning me that if I showed up with another person, or attempted to have more than 1 person in my room I would either be denied a room or charged for the additional guest. (The tone of these e mails, was not a polite reference to my reservation.) They didn't bother me, as I had no intention of having another person share my room-- but Europe, it seems, does take room capacity/rates seriously.

PS-- The times I received those e mails, I was generally upgraded to larger rooms/suites anyway as a Platinum upon checkin