Sarah Jane - Bane of the Bane Again?

Hi folks.
OK, so as it happens, I'm currently killing time before I go and watch the first part of the last story in the latest Series of Sarah Jane Adventures. Childish, I know, but it means I get some of the Doctor Who in-jokes. And at least I can say I watch TV of some kind.
And the plot revolves around possibly the third worst-kept secret in the Whoniverse. The first was Rose leaving at the end of Series 2 (I still cried, even when I knew it was coming), the second was Rose coming back at the end of Series 4 (I still cried, probably because I knew it was coming). The secret (or not) this time around is that Mrs Wormwood of Bane fame is back. And she's teaming up with the "last Sontaran", Commander Kaaaaaaagh. This annoys me, on two levels.
One, how come it is not in the BBC's capacity to keep secrets? This time around it was especially rubbish, as they actually announced it in a press release before the series had even started. But time and time again, the predictable plot has always been spelt out to us by the tabloids: The Master returning, Davros coming back, the Doctor regenerating... Don't get me wrong, they haven't been total letdowns. The Genesis Ark of Series 2's finale was kept brilliantly under-wraps until it was aired. I, in my naievety, never figured it out until those millions of Daleks were spat out all over London. So why can't the keep the spoilers that matter a secret?
Two, the end-of-series "Big Bad", or should that be "Big Bad(s)" this time around, are once again returning characters. Last year's Slitheen I could understand, because they're bound to be out causing mischief if left on their own. But I could swear Mrs Wormwood burst into particles or something in Invasion of the Bane. And Kaaaaaaagh? One Sontaran? I mean, don't get me wrong, they're cool and everything, but your average Sontaran is comparable to your average Cyberman, certainly not able to take on the world by themself. They're foot soldiers, not elite Daleks. And even if he is a Commander, they're clones. Surely they should all be just as good as each other? No, returning villains is a Russel T Davies thing, and it's his one weakness. When Steven Moffat takes over, will be A a lot more creeped out, and B a lot more interested. The aliens will likely be all-new. I hear there's plans to kill off the daleks within the first 6 episodes of Series 5. We'll see...
I could have talked about Christmas here as well, but I'll save it for tomorrow. Right now Mr Smith is calling from the attic, and I've got some Bane to battle! See you all next time!

Jack