I have read that many Bomber Command pilots forbade the gunners from firing but insisted they simply kept close watch and gave him the corkscrew left or right command.
The policy varied from Group to Group as well as among individual crews. 5 Group adopted a very aggressive policy, firing on any suspicious aircraft. Investigation showed that this did not reduce their losses and led to a significant increase in 'friendly fire' incidents.
Many crews believed that the best defence against a fighter, once seen, was to instigate a corkscrew as quickly as possible. This often had one of two outcomes. Either the night fighter lost the bomber in the darkness or, finding the manoeuvering bomber a difficult target, set off in search of another target with a less vigilant crew.
I have read a couple of accounts in which an experienced night fighter crew attempted to follow a corkscrewing bomber, but both conceded that it made an almost impossible target.
Many gunners said that they saw their role primarily as look outs, hoping to see any approaching night fighter before it could launch an attack and in time to warn their pilot so that he could instigate the evasive action. This is what made 'schrage musik' so dangerous, the fighter, in the hands of a skillful pilot, could make an unseen approach.
Some gunners have claimed that a quick and not necessarily well aimed burst in the general direction of a fighter was enough to put it off, again sending it away to seek a less alert victim. On the other hand the bomber, by revealing its position, might attract the attention of any other nearby fighters
There were many different reactions to the sighting of a night fighter, but both Bomber Command and most crews agreed that the bomber's best defence was darkness, not its guns.
Cheers
Steve