Following a Freedom of Information request by Roger Howell, Ofcom made their database of amateur radio call signs available for download
The database, released as a spreadsheet containing 141,296 rows, shows the status of UK amateur call signs as at August 12, 2019.
It can be useful for people wanting to apply for a specific call sign as it shows all those calls which are not available.
Ofcom clarified the meaning of their call sign status field e.g. 'Reserved' means that the callsign has been used within the past two years, although it is no longer, and is in the process of ‘cooling down’. It is therefore not currently available for assignment to anyone else, but operators will be able to apply for it again after the two-year period has expired.