Recently had a couple stays at the JW Marriott Grosvenor House in London, UK. Our first stay we were given an upgrade to a Premium Park View suite without an SNA request. When returning to London 3 nights later for 3 nights, we initiated a SNA request and were given the choice of rooms to redeem for if available. We were cleared and upgraded to an Executive Suite (absolutely fabulous btw) a couple days in advance for our stay. This was our first experience using SNA certs being a legacy MR member.
Happy to say I was pleased with the process and the outcome. The experience at the JW didn't disappoint either!