@AnotherEmma
Thank you, I appreciate your trying to help and recognise that your advice is good for many people.
I'm afraid I just didn't explain the full story. I'm 8/10 over my hips and hate being larger on top. I'm probably a medium size on my top half.
One thing I can promise, though, for anyone else reading this, is that Rigby and Peller don't make mistakes.
I've been going there since the 80's when as a highly embarrassed young woman I turned up in a puffer jacket. Having seen me only wrapped un in the big coat, the fitter brought me an initial bra to 'try for size' and it was the perfect size.
I was blown away.
One of the reasons that they don't use tape measures and fit by eye is exactly how hung up it is possible to get on a particular size, when different manufacturers use different measurements for different sizes.
In order to get a really good fit, which R&P guarantee, they go by how the bra looks and feels. They also adjust the straps so the fit is perfect.
I go for a fitting anytime I've lost or gained a significant amount of weight and otherwise buy online. I've worn the same model (Prima Donna Deauville ) for ever. Occasionally to work around specific clothing i get something different but otherwise ...