Might be worth popping into Marks and Spencers for a bra fitting. I plucked up the courage and went to be measured a few weeks ago. I was one of the many women wearing the wrong size bra and since being measured now don't 'wobble'. After measuring they select a bra in the correct size and check that it's fitting correctly. They're really helpful. You might need to book a time for measuring, depending on how busy they are, but go and have a chat to them and they'll tell you if they can help.