If you are going to buy a 32 band, a D or DD are going to be too small.
You said the 40D and the 38DD fit nicely in the cups. The equivelent of those cups in the 32 band is a 32FF.
If you get a 32D it would be the same as getting a 40AA with a tighter band.
If you get a 32DD it would be the same as getting a 40A with a tigher band.
You would need a 32FF u.k sizing.
If you breasts fit a 40D cup there is no way you could fit a 32D cup. Its 4 cup sizes smaller LOL
Also a 32D is about 1inch different in the cup than a 32DD.
Hope this makes sense to you.
try a 36E
You get a different pitch and resonance when motorboating.
the cup size is different. Go and get measured again and make sure what they say is right, then have the correct size ordered. If you wear the wrong size it will be uncomfortable. the number is how big around you are just below your breasts, the "D" is the cup size.
here is a video on how to do it yourself:
The numbers mean the size of the band that goes around your body. The letters mean the cup size. the larger the number, the larger the band size. The farther down the alphabet, the larger the cup size.
Get in between, 36D. for some reason the cup is made a tiny bit larger so it's not quite a DD, but still fits well.