I don't understand Bletch's logic when he declares that it was a misuse of bombers "stooging around looking for U-boats" when in the same sentence he boasts of the RAF's U-boat kills. U-boat kills were by definition the result of looking for U-boats - much better looking for them around the convoys than under 25 feet of reinforced concrete in the Lorient pens. Although a relative of mine won the DFM over Lorient, I suspect much of the attack on the U-ports was an exercise in battering the bombproof fortifications. And - Coastal Command was part of the RAF! This is a shocker! BTW, where do you get the idea that only 1 was sunk by air attack?
Indeed, U-boats tried to operate outside aircraft range in "The Gap" half-way across. But Bomber was resistant to allowing Coastal to get their hands on the types that could operate into the Gap - specifically the Liberator. Once the VLR Liberators were available in numbers, the convoy loss rates plunged. The U-boats of WW2 attacked primarily on the surface at night - aircraft with centimetric radar, the Leigh Light and sufficient range could effectively remove this as a possibility all round a convoy. The real index of success in the Atlantic was the loss rate of merchant shipping - this was an offensive task strategically because it permitted the build-up of UK, US deployed and Soviet power that would do Germany in.