I don't think you should see it as Vodafone blocking you from other services, but other networks choosing to block access based on a list operated by a third party.

It might seem like the same thing, however, as I understand it, the networks only voluntarily agree to block IMEIs reported by other networks. So in theory, any network could accept your phone if they wanted to. Obviously they wont, otherwise there would be no point in the IMEI blocklist, and I think this is a decision that you're going to have to accept.

You have the physical item, which as you say is legally yours. That doesn't mean that any network has to necessarily accept the phone onto their network.