Quite clearly there’s a big William Blake motif with the title of the story being In the Forest of the Night and the use of tigers. People are also seeing an ecology message with the infiltration of jungle.
My suspicion is this story, by Frank Cottrell Boyce (several children’s novels, dozens of screenplays) is where Danny gets to become a real companion of the Doctor as he will prove himself during this story.
Isn’t it curious that Coal Hill children happen to be the one’s at the focus of yet another adventure? Would you send you kids there? Missy also pops up and I assume this links to the two-part finale. I’ll leave you with Blake…
Tyger Tyger, burning bright,
In the forests of the night;
What immortal hand or eye,
Could frame thy fearful symmetry?
Watch out for that symmetry!