Actually, the Dutch and English versions are more than likely not compatible at all. All electronic media, from DVD's to electronic downloads, have region codes. For DVD's, these codes have to be compatible with the machine you play them on. For example, I couldn't normally buy a DVD from Japan, because American DVD players have different hardwired region codes. However, this is not an issue for me since I spent extra money for a DVD player that was does not have hardwired region codes.
Games with expansions are different. There are different patches for different regional versions and it's probable that, due to this, the game will not allow you to install an expansion with region codes that don't match what is already installed on your computer. Patches that are downloaded are applied to all the expansions that you have installed simultaneously, and since the region codes for your expansions would not be the same, none of the patches would be compatible.
Edit: What I meant to say by all of this is that it's quite possible that Origin would know the difference between a Dutch activation key and an English activation key. While I do not know for sure, it's possible that you could either end up downloading a Dutch version anyways or that it will tell you that the version you are attempting to download cannot be downloaded in your region.