I really felt for Alex and agree she may have just had enough and be in pain and exhausted.
George was excellent, really stylish and characterful. Wish they'd give him grown-up dances and costumes every week; he seems happier in them than doing the 'yoot' thing.
I liked Balvinder! She had good kicks and good leg action. Excellent acting too.
Karen was fabulous, although I don't really like that type of dancing. I'm getting 'winner' vibes from her and Carlos already.
Lewis and Katya's was a bit of a contempowaft. Interesting that the judges didn't comment on that whereas they did on George's similar rumba.
Didn't much like Amber. I'm sure she went wrong near the beginning, and her style is too balletic, light and not into the floor enough.
Instant Dance came across to me as a lame attempt at livening Strictly up and making it into an 'adventure' type show. The silly little screen at bottom right showing them running to the changing rooms 
Didn't get the little skit of Claudia 'helping' them with their costumes either; I mean, I get that she was probably briefed to make sure they picked something vaguely suitable for the dance, but as entertainment it fell flat.
However, I LOVED Balvinder; never seen her so ferocious. I think she feels she's got nothing to lose.
No one else really stood out for me. I was annoyed that Lewis still had those wild uncontrolled kicks in his jive but the judges didn't mention them, despite critiquing them first time round.
I think it's likely it'll be Alex and Bal in the DO and they'll save Bal, unless Alex miraculously remembers all her steps and gets some painkillers and an adrenaline shot. But possibly Alex and Amber, depending on how the voting goes. I'd love to see the audience vote from last week.
EDITED for typos and to add in about the clothes selection, which I forgot to say.