Gold Choice has been around in Europe for many many many many years and this is the way it works. If you see a car in Gold Choice that you like, you can ask to swap with one of those vehicles. If it’s the same class, they’ll give it to you free and clear. If it’s an upgrade, they give you an upgrade price.
It is NOT Ultimate Choice like the US. I’m not quite sure why you would think it was the same, especially with different namings.
Either way, I’ve found that most European locations will provide you with an upgrade if you politely ask for FOC. Sorry you didn’t have a better experience. We’re you nice once you learned about the upgrade charge and that it was in fact a different program than Ultimate Choice, or were you upset and condescending? This would easily affect the way they treated you going forward and their willingness to support you.