Can't install app as my phone is in 'wrong country'

[Guest Kaiser Wilhelm II]

I recently upgraded to a Xperia Play (great phone) but decided to upgrade my old San Francisco to Froyo to gain benefits like App2SD support (and for the fun of tinkering with it).

All is good with a few minor problems (occasionally the touchscreen will just seem to die after a reboot).

However, I have a niggle when trying to install the BT Fon app. I can't see it in the market from my SF but when I go to the web version of the market and check it there I get informed that

This app is compatible with some of your devices.

Vodafone ZTE ZTE Blade

This item cannot be installed in your device's country.

Now, as it happens I have a Republic of Ireland SIMcard in it at the moment but is it that, or something in the MoDaCo r12 Froyo ROM that is preventing me from installing the BT FON app. i.e. How does Android determine what country your phone belongs to?

I'd like to put the app on as I get free connection courtesy of a home BT broadband connection. The app runs great on my Play (UK Orange SIM).

[Guest Kaiser Wilhelm II]

Just to add - got an app called 'Market Enabler' that let me spoof a UK provider and got the BT FON app installed.

I would still like to know exactly how Google determine what country your phone 'belongs' to though ... some say it is IP but maybe it's part of the ROM or probably the simplest answer, the SIM card.

[Guest targetbsp]

I would still like to know exactly how Google determine what country your phone 'belongs' to though ... some say it is IP but maybe it's part of the ROM or probably the simplest answer, the SIM card.

The description of the Market Enabler app tells you in the first line... (sim card) :)