A 42 band does most of the work — around 80% of your support comes from the band, not the straps. If it rides up at the back or the straps dig in, the band's usually too loose or the cup too small.
We stock a 42 across the full cup range — 42D to 32K — graded for fuller busts. Not sure of your cup? Book a free fitting and we'll get your 42 sorted.