For example we have just seen Janette with Jake waiting to see if they get through to the ifnal and now here she is performing to Paloma Faith.

I know it is all edited for the telly, but at what point would the guests in the audience see Paloma Faith perform?

the guest singer is filmed before the live show on saturday night

Cheers for that.

And why not use one of the eliminated female pros for the dance instead?

Because they go and tear ligaments

Not every single one of them.

Aliona, Natalie, Joanne and Iveta are all still available to dance.

I thought Aliajz danced with Joanne in the pro dances.

Aliajz has done Steve, but his usual partner is his girlfriend, Janette.

There's a fan-fiction in the making.

Lol! Well spotted, and lucky Steve :P

Janette's not his usual partner, in fact she and Aljaz rarely dance together (they were particularly excited about the Halloween week pro dance where they did dance together) except for the odd dance to guest artists that's usually vaguely a Rumba, and the odd bit of partner swapping in pro dances. Janette is too short to be a suitable dance partner for Aljaz really, and they didn't dance together when they were in Burn the Floor either. They do showdances together in the off-season, but presumably not any involving ballroom!

There are no fixed pro partnerships this year, and Janette is more often than not the spare who disappears halfway through a pro dance.

As for Janette being Ola's replacement instead of any other female pro, my guess is what we saw tonight was something that was already in Janette and Aljaz's repertoire, so required little rehearsal time and didn't involve anyone having to learn a new routine.

It has even been known for the guest artist to be recorded the week before broadcast or even during the week before broadcast if they aren't available on the night.

The pro dance routine perfomed on last week's results show (splashing around with the water) was, I thought, filmed on a separate day. I thought some of the pros had tweeted about filming it.

That routine is here: http://www.youtube.com/watch?v=rH5S5seec5I

As the camera pans around there are some brief shots which do include an audience. At 2 mins 10 secs you seem to be able to see almost the entire audience on the right side, and at 2mins 15 secs you can see the audience on the left side.

I don't know if that audience was people brought in just for that performance, or artificially generated some way (perhaps merging images of the live audience from another show, though they do seem to be clapping in tune).

There was a lot of cheering and clapping throughout the performance. I don't know if that was real or synthesised.

Yes, Lady Gaga and Tony Bennett was filmed a couple of weeks previous to when it was broadcast, IIRC.

Some earlier dances had CGI use so would have been filmed the week before. The show I saw had the correct studio guests but there was no Sunday night opening sequence.

Worked at the beeb in the distant past, and sometimes what would happen with things like this when a segment is being filmed mid-week, they'd send an email around to staff in the same building saying audience wanted, and people who fancied a bit of a show in the lunch break or whatever would turn up and fill the seats. You can always rustle up an audience from somewhere!

actually I don't believe she is, Aljaz is dancing with Joanne during Strictly, I don't think Janette has a partner as there is an odd number of male pros

I don't think they danced together when they did Burn The Floor either but someone who saw the show might need to clarify that

None of them have fixed partners this year, quite a few of the pros have mentioned in interviews that there's a lot more swapping around compared to previous years.

And I think Janette has said herself she didn't dance with Aljaz on Burn the Floor (there really is too much of a height difference). Kevin and Karen didn't initially dance together either - Aljaz and Karen said a few weeks ago when their pro challenge was shown that they used to dance together on BTF!