Sunderlands were banned from landing to pick up survivors fairly soon after the start of the war as so many crashed in the attempt. It is difficult to judge the height of waves from the air and you don't get a second chance. I know a number did but it was unofficial. It was the dear old Walrus that used to land to pick up people. That takes guts.
A small story was in 1944, a Walrus picked up an American out of the sea and discovered his base was on the way home. They landed at the fighter base and no one came out to meet them. After a while a jeep hurtled up to them, slowed almost to a stop, drove slowly around the Walrus. The officer simply shook his head, muttered 'Dear God' and drove off again.
Re the Anson. I remember reading about this. It was a long time ago but if I am right it was the CO of a squadron who upgunned it with a 20mm throught the floor, waist guns and at least one extra mg in the nose. I could be totally wrong but it does ring a bell in the back of my head.