The DVDs are not based on the BBC HD master. You can tell by the Raiders shot with the Jeep flying over the edge of the canyon - the DVD and the Japanese HD version use the original theatrical matte, while the BBC HD version uses the CGI-replacement matte first seen in the SciFi Channel broadcast.

You said the Japanese version has hard subs - could you post some screens of those? I'd like to know how easy it would be to remove them.

The BBC HD logo would be super easy to remove, as it's entirely within the letterboxing, but as I said, it's not the original version (at least for Raiders).