Yes I think in previous years the performer has gone out on the balcony to talk about how the concert was going with the presenter. I assume Nile Rodger’s speech about his health accounted for this being cut?
I'm sure that's not been the case - I remember having this exact same conversation when Queen did it the other year and they were still doing The Show Must Go On until about thirty seconds to midnight. But there's absolutely no way they would have overrun into midnight. It wasn't like they were doing improvisational free jazz, they've performed these songs hundreds of times before and know how long they last. The other post said that it went to Big Ben with fifteen seconds to go, but they were there by midnight, so what's wrong with that? The options are performing right up until midnight, or stopping with minutes to go but then you have an awkward gap - and I can't think a couple of inarticulate vox pops would be any more exciting than the band continuing to play.
I'm afraid I simply can't believe that Nile Rodgers and his band would have blithely performed through midnight. They're professional entertainers, their set list was approved and they knew why they were there. It may be the case that the timings were a bit tight because people wanted to touch Nile or something, but there was no way they would have kept going.
And even if they did, there's no way the Beeb would have missed midnight.