The bra I found the most useful and could not have managed without was a crop front fastening soft bra from George at Asda! It looks like a sports bra, but isn't. I needed my boob to be supported without being crushed or pushed into a position. The front had around 10 hooks and eyes and I found just fastening the bottom 2 or 3 was enough. My wound site was on the inside near my cleavage so this prevented any pressure on my wound. The straps are wide and racing-like at the back, so nothing hurts or digs in. It just gave me gentle support. Because your boobs move all over the place, you have no control over them and your wound will move with your boobs, this hurts! This bra really helped. I wore it for at least the first 10 days.
When the pain started to ease a bit I moved onto "Post Surgery" bras. If you haven't had a Mastectomy don't be put off by the linings which contain little pockets that are there for falsie boob bits, dismiss it from your mind! The bras are very soft, no wires, and they are pretty and feminine and give support without hurting your wounds. I tried lots on to make sure the fit was right. I didn't want an "old lady" look where your boobs are too pointy or too droopy! I did have to sacrifice the droopy look a bit, because that is simply where having no underwires takes you! However I did not mind this at all. Comfort was all I cared about.
Asda George Post Surgery Bra