Hello again kitbag, I'm not stalking you honest!
I love the 2 for 1 rate. It depends on which hotel you stay in whether you get qualifying night status and points or not, if you do it will count towards Sweet Dilemma. I find I've had less success getting qualifying nights with HI Express compared to Holiday Inns. For the 2for1 rate they charge you full price for 1 night and £0 for the 2nd night, so technically you should get 1 qualifying night, 2 if you're lucky. I've tried filing for missing points with mixed success, less success of late!
There is a thread on here somewhere dedicated to people not getting points for 2 for 1, but can't find it at the mo.