The highway code applies to anyone using the roads. (Including cyclists!) A new version is due to be released in print in the next few months.
I remember doing a cycling proficiency years ago but some rules are the same. Cycling proficiency is now replaced by the Bikeability course. Check your regional council departments for details.
There is also a website for training information children and adults:
https://www.bikeability.org.uk/
References on gov.uk:
https://www.gov.uk/government/news/the-highway-code-8-changes-you-need-to-know-from-29-january-2022
https://www.gov.uk/guidance/the-highway-code/rules-for-cyclists-59-to-82
