I'd like to see dramas like this be successful, if it means that BBC4 will start to commission more of this kind of thing.

Yes, absolutely. I suspect BBC4 may start to fulfill the same kind of more risk-taking role that BBC2 had when it first started up, and if things they commission end up on one of the main networks as The National Trust (though I'm not sure if that was originally a BBC4 commission) has, then I'm sure all parties will be very happy.

I can't see what BBC3 offers, to be honest - but then I'm not its demographic, I guess *g*

I'm not sure anyone is *g*.