I read Trillions years ago to my oldest son and during the conversation we had about it afterwards - 'bedtime' talk was always about difficult questions so that he could avoid going to sleep - which was pretty much about Space/ Hyper-dimensions/ Parallel Universes etc - it struck me that Nicholas Fisk is pretty much describing Terence McKenna's DMT-inspired Self Transforming Machine Elves.
I'm not gonna explain. If you've got kids and you can be arsed you'll see what I mean.
It's a great book to read to little kids, though... they can tune in. They are self-transforming machine elves, munkins, mad-things already and they're open to persuasion.
There's a general peace, love, 2001 A Space Odyssey vibe permeating through Trillionas which goes some way to reinforce the idea that maybe this is an intentional steal (it was written in 1971 - at the peak of the flash, so to speak) and about 7/8ths through the book there's a sequence of pure psycho-gealed hyper-dimensional fun and frolics that should leave no question that Nicholas Fisk is a space-cadet of the lowest order.