6.20pm is the absolute best time to put that show on, to catch all viewing ages. Be interesting to see where they've cut 20 mins from as well, as the tv version runs to around 65mins, and the stage version came to just under 90mins.
There at least 10mins where the cast speak with the theater and have a sing a long etc.
It's a shame it wasn't practical to film/record a performance in the theatre, though having seen it (and unplanned got my programme signed pre-show) the theatre is fairly small. Some of the pre-show stuff is also very funny. I dare say the odd bit may get toned down slightly for a BBC One family teatime audience.