Beyond Selidor

They all have storylines, but some of the storylines are more detailed than others.

I suspect part of the reason why they do London in the winter is that they use an indoor venue (i.e. the Royal Albert Hall) rather than their usual massive outdoor temporary tent — which would be miserable for the audience in a London winter (obviously the tent is warm inside, but you have to queue up outside it, and food/merchandise stalls are open to the air).