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.
Bra sizing
As far as I am concerned bra sizing is a whole rant into itself.

I think US and UK bra sizes are similar if not the same. According to the usual way of measuring it (measure under the bust, add 3" for the back size, measure round the fullest part, take the difference from the back size to work out the cup size) I come out at something ridiculous like a 42DD. In practice, though, 38D fits me perfectly well....MOSTLY. It would be very nice to be able to walk into a shop and buy a 38D and know that it would fit (actually that goes for any clothes, not just bras). Some 38Ds won't even fasten around my back, others will fasten but cause humongous bulges over the top of the cup... I could go on.

Plus, Marks & Spencers brought out a fantastic range called something like "Flirt" a while back which was supposed to be nice bras in larger sizes rather than the usual cantilevered constructions with 17 hooks and 5 inch wide straps. I bought several bras from that collection that were absolutely wonderful and then they went and withdrew the entire range! Sigh. In fact one of those ones is the one I'm wearing today with the freshly broken underwire. :-(
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!
Re: Bra sizing
Yes, I think our bra sizing is basically the same. I forget the exact formula for figuring it out, but it sounds *very* close at least.

I hate the cup-top bulges....Jim calls me "four boobs" when that happens. :-)

it's still very strange for me to have problems finding bras that are big enough! Back before I gained all this weight, I was barely a A cups were always too small and B cups were often a little big. I dealt, but something like a Wonderbra was the only thing that would give me any real lift. But now, as I've gone up a band size and a cup size, instead I've got the opposite problem. I'm swimming in a D cup, but C cups are often just a wee bit small. I'm hoping as I lose weight that my body, true to form, will decide to ditch the excess boob fat first, so maybe I can have a fighting chance at finding good bras!

I've really gotta go out and find The Perfect Bra -- and then buy it in multiples. :-)