Isn't it amazing how situations like that can happen so commonly, and they usually only happen with official organisations, and when Britain, and especially a British Governmental Department is involved, it's not hugely surprising.
You have a credit card, and presumably you also have a bank account, so you will also have a cheque book, or can obtain one from your bank.
If you have a cheque book, ask your bank if their cheques are cashable within the British banking system, and if they are, no problem, unless the MOD won't accept cheques for foreign currency, and you would have to ask the MOD what their policy is in that regard.
If they aren't, then mztiz1's advice is the best course to follow.
An international money order or a cashier's cheque may suffice.
In Britain a cashier's cheque is called a banker's draft.
However, before you try any of those methods, you should first check with the MOD to see if they will accept the payment method of your choice.
The MOD Information Rights team deals with complaints about how applications for British military service records were handled by the British Ministry of Defence, so they will probably be able to tell you what forms of payment are acceptable to the MOD.
cio-foi@mod.ukThe MOD in London also has a phone number for general inquiries General enquiries
020 7218 9000
http://londoncalling.co/2010/11/calling-a-london-number-from...http://www.prokerala.com/how-to/call/united-kingdomNo corresponding email address for general enquiries of course. !
You might do better with a specific answer to your question about previous overseas applicants, if you posted that enquiry on an Australian message board, there are lots of of descendants of British expats and British vets and their descendants in Australia.