Granee Bravissimo don't even use a tape measure, they look at you and bring you about 6 bras into the fitting room ... and work from there. Fitter asked me was it ok for her to adjust the straps, hooks, check the fit of the wires against the breasts.
You should also do the 'scoop'. Bra on and then scoop each boob right from underneath your arm, scoop it forward and into the cup. There should be no spillage under the arm, or over the cup. At the front - the centre should be touching your breast bone with no spillage from the cup and no '4 boobs'. There is also a design feature called the sling in some bras which lifts and supports your breast lifting it up and forwards. When I got my first one fitted I felt it was much too tight at the back, really too tight, and I insisted on taking the next back size up. How wrong I was. In no time at all the back was creeping up even in the tightest hook.
The secret for bigger boobed ladies is to get it so that when it is fitted on the loosest hooks it feels almost too tight. Two or three wearings later it was perfect. Gradually as the bra stretched I wore it on the middle hooks. I'm now using the tightest hooks and it's still great.
My best fit comes from Bravissimo own range at £30 or at a push Fantasie which runs about £40.
Once you've found a make and style that fits then they can often be found on line.
Minimiser bras I've found to be shapeless, they just push the breast tissue around to under the arm.
Good luck to everyone seeking a bra that fits 