After swimming lessons at school, age about 12, when some of us first started wearing bras, the girl I shared a cubicle with put her bra on upside down and inside out, fastened the hooks at the front and then twizzled it round, arms through the straps and bingo! Job done. Not fiddling about blind behind your back. I copied her and have done it that way ever since. Since babies and menopause I'm a G cup ( not sure what that is in UK sizes) and I am really grateful for this method.
Leaning forward to settle into the cups is one of the tips I picked up working as a Saturday girl in the lingerie and corsetry department of a department store. I wish I could remember more about it.