Platinum Concierge has rarely failed me overseas. Most of my year is spent in Australia and the agents working overnight (in the U.S.) responding to my requests via SMS seem to know more about local restaurants and have connections than my friends. Numerous times they've secured tables at the last minute. Use Concierge more here than the U.S.

Also, if they can't figure something out, they'll sometimes call the Australian American Express office.

Surprised they responded to your castle rental and bus tour requests. They're trained to direct travel-related inquiries to Amex Travel