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