Grateful though I am for the wonders of underwire, I do NOT like it when it breaks and tries to poke a hole in a rather sensitive place. Ow.
Re: Bra sizing
I thought it was "add 4 or 5 for back size to get an even number" not add 3? Although that would then presumably make you a 44C, which you'd be no happier with. Mind you I usually say "add 4, and if it's between sizes try both and see which is more comfy".

By the tape measure I'm currently a 40B, which is probably about right at the moment actually, the 40Cs I have are too baggy in the cup and the 38C I bought optimistically is marginally too tight around the chest and a little tight in the cup too.
Re: Bra sizing
Hmm, a quick Google confirms you are right (I thought it was 3 or 4 rather than 4 or 5). Still, as you say, that makes it even more wrong for me!