There has been a change to the regulations regarding laps out in circuit races, and it is important that all members who race are aware.
Riders now cannot take a lap out (for a puncture, mechanical etc), as it was deemed difficult to manage and open to abuse. If you puncture you have to make it to the pits, change a wheel, rejoin the race and chase back on.
There is no mention of crashes but we can assume there are no laps out full stop, even for crashes. If British Cycling clarify the ruling in the future we will update you.
The regulation changes can be seen at https://www.britishcycling.org.uk/zuvvi/media/bc_files/officials/QG_-_2017_Reg_updates_-_General_Road_Track_and_Roller.pdf