Half of them regulate marketing authorization issues such as

• the renewal of marketing authorizations
• the licensing of biosimilars
• the handling of master files of active ingredients 
• the registration of new packaging information

Another set of documents deals with import and export.

A large set also regulates supply in Northern Ireland, which remains subject to EU law.
In addition, the National Institute for Biological Standards and Control (NIBSC) has also published documents. These address the changes associated with the UK's exit from the EU Official Control Authority Batch Release program (OCABR).   

OCABR certificates for the supply of biological medicinal products in the UK could be used until 31 December 2020. All certificates issued up to that date will remain valid. Future batches will need to be certified by the NIBSC. Exceptions apply to products tested in countries that the UK has MRAs with. This currently only applies to Israel (for vaccines only) and Switzerland.

Here you can find an overview of all documents. The MHRA website is updated continuously.

Sources:

MHRA: New guidance and information for industry from the MHRA

NIBSC: Guidance for manufacturers of biological medicines - independent batch release in the United Kingdom