Yes, dsawan, but with all due respect, wiki is hardly a concrete reference source for WWII aircraft (or anything for that matter).
This is great that you have taken time to give our Beaufighter a makeover, doc. 180rpg on the 20mm is probably correct, as there is a lot of room back there. However, the pilot entered through the floor of the aircraft about a third of the way down from the nose and made his way forward through some armour plated bulkhead doors, so the ammo tanks would have to have been arranged so as to not impead the pilot. The breech blocks for the cannon were just aft of the bukhead. Another reason I can't imagine a third crew member, as he would have to have sat with the bulkhead doors open.
Even with two crew, can you imagine the pilot trying to exit a burning, diving aircraft? Near impossible I would say.....
n