The FCA, regulates listing of companies for trading on UK stock exchanges through the UK Listing Authority.
Its main role is to maintain the Official List. This is simply a list of all securities it has approved for trading on exchanges in the UK. It also maintains a list of the issuers of those securities.
The UKLA also sets the requirements for listing and the rules for procedures and documents related to listing, such as IPO prospectuses.
The key information published by the UKLA can be found on the UKLA website.