Actually, given that a call from many UK plans to the USA is far cheaper than a call to a 0870 number (and how ridiculous is that ), and since I believe this is a world-wide account, you might try calling their 24 hour HHonors Customer Service Center on +1-800-449-4155. Even though it is a 1-800 number, you will (unfortunately) have to pay for the call.

There is also a number on their US web site for the UK - 0141 3041006

Of course, just to rub in the Rip-Off Britain bit, if you are in the USA or Canada, HHonors members call toll-free 

The above 0800 number appears to be to long? But if its any help to you the card is run by HFC Bank(Beneficial) whose operations centre no is 021 233 4477.They might be able to put you through.Good luck.