BBC HD and Being Human

[shoggoth1]

I'm sure the first series of Being Human was broadcast with DD 5.1 but the recent 2nd series has been 2.0 - the 'cut pieces' between programmes are still 5.1.

I think a similar thing has happened with Shameless on 4 HD.

Anyone else noticed this/knows what's going on (I'm guessing saving bandwidth)?
(This is with Virgin V+).

[shoggoth1]

Further to the above, I got around to watching the final episode of Being Human last night and that was in 5.1. The previous ones had been 2.0 - honest.