Just finished reading Trillions to my youngest son and during the conversation we had about it afterwards - at the moment our 'bedtime' talk (i.e what he asks me about to avoid having to go to sleep) is 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.
There's a general peace, love, 2001 A Space Odyssey vibe permeating through the whole book 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 psychogealed hyper-dimensional fun and frolics that should leave no question that Nicholas Fisk is a space-cadet of the lowest order.
On the other hand I'm not at all sure about this.