Found: U.K. Sci-Fi; Alien visits Earth through the eyes of a boy

(Science) Fiction work I read in the 80's about a young boy who gets a visitor from an Alien. The boy hears the Alien's voice in his head, and chat while the boy grants the alien a guided tour. At one point the alien laughs at the boy's car, insulting the crude technology "It's held up by SPRINGS ha ha" and the boy becomes apoplectic with rage ("It's a jolly GOOD car!"). At this point, the kid's parents know this is beyond the run-of-the-mill imaginary friend thing and seek help. At some point the boy somehow gets to visit the alien's world too.
I described a lot of this to my son, whose eyes lit up and desperately wants me to read this to him, but for the life of me, I can't find it, or remember other google-able details. Halp? TIA!

Chocky by John Wyndham.

EEEEEEEEE HOLY HEAVENS THAT'S IT!
*cough*
I mean thanks! That's particularly fantastic of you, and exactly correct. My son and I thank you!

Yeah, page 42 She said the engine is funny, and old-fashioned, and wasteful, and that an engine that needed gears was ridiculous anyway. And that a car that didn't use an engine to stop itself as well as make itself go was stupid. And how it was teribbly funny to think of anyone making a car that had to have springs because it just bumped along th cround on wheels that had to have things like sausages fastened around them.

It was on the shelf right behind me :-)