Huh, that's odd.
My problem was the promo code was invalid - even while using a VPN. I figured it must be because I initially made my account without using a VPN (didn't know this was region-locked at first) and sure enough, that worked.
But 'not available in my country' is really strange. Don't know what you can do then.
I know there was a list of countries you could choose when you signed up, which country did you pick?
No idea what I did but it worked.
Made a UK account with UK VPN. Accepted the promo code but got "not available in my country"
Made a German account with German VPN. Accepted the code but got the same message.
Made another UK account like the first. Accepted the promo code but same message.
Made another German account like the first. Accepted the promo code and the order finally went though.
The email I originally used to signup with was under a UK VPN and I said I was from the UK when it had asked, yet the code ended up working on a German account.
This is how I did it first time acquire tips from SG. Pretty simple.
1. Create an account.
2. Entered UK address
3. VPN is enabled on Chrome before visiting website again
4. Add Dark Souls to Cart.
5. Checkout w/ Code
6. Shows up 0.00, Place Order
That's it, enjoy dying!
Exactly what I went through. Every time it accepted the address and the promo code while I was under a fresh browser running the relevant VPN. The order would show up as 0.00 but when I placed the order it would process for ~3 seconds and then I would get a message saying I either owned it(which I didn't on Steam nor in my Golden Joystick Store library) or that it wasn't available in my country. I would then check my Golden Joystick Store library each time it said that to see if it added it anyway and it didn't.
Regardless I finally got through the multitude of hoops and finally got it. Thanks for the help!