The good news is that each of the hotels have agreed to refund me the "calculated difference" in exchange rates between the DCC exchange rate and true foreign exchange rate on the day. Interestingly, each of them are going about it in a different way. I think I'll likely still lose some money in the end, but at least some action is being taken. And to each hotel's credit, the front office managers have worked with some urgency in resolving my issues.

But you're right, this has been a valuable lesson and I'll be carefully scrutinising all paperwork I sign from now on.

I will also be sending an email to Simon McGrath (COO Asia Pacific) about this, once I have finalised my refunds (received paperwork) from each of the hotels.