I read a series of books, probably around 1962 - 1970, about some young kid (a teenager) whose name I think was Chris.
There was a problem with the Moon, it was being invaded by a mould (mold) which was some sort of threat to the Earth.
For some reason, only a single person could go in a spacecraft to deal with this threat, and Chris was chosen.
He had a few mentors, there was a friendly one, and a "harsh" one, who Chris thought hated him.
In one of the books, his rocket ship became disabled, and one of the adults had to fly up to save him. He naturally thought it would be the "friendly mentor" but it turned out to be the "harsh mentor" who actually had a high regard for Chris, but couldn't let on, because that would endanger the mission or something.
I think it was set in England.
In one of the books Chris was heading towards the space training centre, when he was set upon by some "Teddy Boys" who forced him to lick their shoes (or something similar). One of his mentors came upon this scene and was initially disturbed that Chris was a coward, but he revealed that being beaten up just before flying to the moon would have not helped the mission.
Does anyone recognise these?