I came across this programme on You tube a few months back in six parts starting here
I did not particularly notice the synch issues, as I was watching through a You Tube version, I accepted this as a computer glitch.
If it was as bad as it comes across to me via my computer, sorry it was crap production wise and I do hope it wasn't as bad as that.

The "Guy with the tights", watch the clip at he start, he is one of the "entertainers" he is shown "singing" while the "Belles of London City" are Morris Dancing in the background, during the "pre-show" warm up of the audience. Where else are you going to seat anyone looking like that but right up front and centre.
The whole thing is "Over the Top", it was meant to be, it was aimed at being a "Christmas Revelry". It was not aimed at the "Folk Elite" who know their stuff and write on "Mudcat", it was a light hearted frolic. If BBC keep showing it, it obviously works for a majority somewhere.
Watching it for the first time on you tube I accepted it for what it was an enjoyed an awful lot of it. However there were parts which I could fast forward though, so gladly they do not stick in my memory.
One of which is the "Unthanks" whose tuning and harmonies I can not come to appreciate, they were not the only ones though. They are just the ones which I recognize, having seen them live on a trip to England.
So take the majority of it for what it was, entertainment which was not really aimed at "YOU" but the general public.
If you want better original entertainment, go to a "live" Folk Club etc, something I am not able to do in Canada as much as easily or frequently as the contributors from England.
JohnB