Good luck to you, but you may as well talk to a brick wall with Vodafone.
I managed to talk them in to providing a username/password for my mum's line many months ago but they have completely clamped down on this. I only managed this as I was advised during the ordering process this would be ok. If you read through all this thread you'll see even complaints to the CEO office have no impact.
NewtronStar's case summed it up perfectly. It was very obvious that his circuit was very unstable with the Huawei HHG2500 connected. Vodafone continued to refuse to send over his PPP login details, pointlessly sending OpenReach engineers who found no fault. They choose to release him from his contract at their own expense rather than allow him to use his own device. That's despite the fact the device he wanted to use has passed the MCT.
How is the HHG2500 performing on your line? It wouldn't even hold sync with N'Star, and that's how he got out his contract. You may have more luck if you suffer from similar issues.
The worry would be if this locked in platform became commonplace.
A number of ISP's already do this, Sky being 1 of them. The only difference is that there's a workaround to get Sky's login details.
Hopefully someone will work out how to obtain the PPP login info from this device. I can't see Vodafone changing their policy here.