Ok, just watched the results show. Yes the contestants mimed the intro part, but that was it - this is easy to tell, because they were all in tune.
You could easily hear Whitney out of breath every few seconds, so at least she was doing her job.
Now then Shirley Cole? Mimed quite well I guess - She didn't really...
Tbf, she attempted to adhere to the 3 golden rules taught at mime school.
1) Hold the mic as close to your own mouth as possible to help conceal bad lip-syncing to the pre recorded track.
2) Make sure the director does not do close ups and if he does only for half a second.
3) Repeat rule one - alot.