Chloe Annette's portrayal of Kochanski is like David Ross's portrayal of Kryten. We take Llewellyn as Kryten well, and think he does a great job. But Ross was the original and alas we won't know how good or bad he could have been.
Claire Grogan however, that's a different matter altogether. I think they tried to get her back for series 7, but alas failed. Hence why the "Parallel Universe" was created.
Ah yes, some great moments. I suppose series 7 missed on the live audience as the other series had before. Who knows, could have been different.