British Nationals
British Nationals are qualified for through achieving a top 30 fastest time in the country during the qualification window from March 7th to May 11th. For over swimmers 18 and older 36 swimmers, with 12 of those spots going to rising 18 year olds.
english nationals
English Nationals typically is the next 26 fastest times in the window, however this is subject to change year to year. The qualification window is the same as the British national window.
Surreys
The automatic qualification time grants automatic qualification, while there are consideration times that may grant entry into the event. However, there is no guarantee that the swimmer will be admitted into the swim meet.
Link to the times here
south east
regionals
South east regionals is very similar to the Surrey Swimming Championships, with automatic qualification times and consideration times, however these are faster. Link to the times here