Getting orders from out of zone customers by check / mo

We are based in the UK and accept international orders. We use PayPal Express and also accept check / money order from customers in the UK.
I've set up a Zone for the UK and set this in the Payments / Moneyorder module so that (in theory) only people in the UK can pay by check / moneyorder. That zone is also set for free shipping if the customer spends over £16.
We've tested this using UK and US addresses and, for us, it works fine and we get UK customers using that method.
When testing if we use a UK address we see PayPal Express and Money Order as payment options. If we use a US address we only see PayPal Express.
Somehow, US customers (our products are popular in the US) still seem to be able to select Check / Money Order as we have had orders come in. :huh: We have no idea how this can be happening.
Help appreciated.

It happened again :(

If we could have a link to your site, those of us in the US might be able to take a look and figure out what's happening.

Sure, that would be great.

www.samburu.com

Well, I created an account with a US address, and I'm only seeing Paypal as a payment option.

Your template doesn't give customers the option to logout, so I can't create another account to test this, but is it possible that visitors are creating accounts with UK addresses, then changing the shipping address to the US?

stevesh:

Well, I created an account with a US address, and I'm only seeing Paypal as a payment option.

Your template doesn't give customers the option to logout, so I can't create another account to test this, but is it possible that visitors are creating accounts with UK addresses, then changing the shipping address to the US?

Thanks for looking stevesh. It is possible to do that, but I think it unlikely as you'd see the invalid address on the order confirmation emails and they are definitely the correct US address. We've tried recreating the orders with the exactly the same data the customers used and can't replicate the issue.
I've been meaning to add proper login/out sidebox so I've just done that. Thanks for reminding me.
I hope we can find a solution as I'd hate to take the check / mo option off because we take quite a few orders that way and its good to give people the option.