I know you said you're using the mobile site, but I would just want to make sure you are. That error message is one you get when you try to download a zip file (obviously) instead of an OTA file.
I just tried it to see if perhaps Beiks had posted the wrong download. But I would assume if that had happened they would have heard about it before now. And my British download attempt showed a proper jad file. I didn't actually go through with the download because I don't need the British file.