Update!!
Thanks for all your responses and Kellie you seem to be right. I went to Bravissimo and the same problem arose, however, she took on board that I was uncomfortable and tried lots of different styles until we eventually found one that gave me the coverage I wanted. They sized me at a 32 E which is different to Rigby & Peller but they felt a 30 was better as a 32 would stretch and be a little loose quite quickly. I think it comes down to preference on whether you want it tight or mega tight.
Anyway contacted R&P to say not happy as I felt pressured and rushed into something I wasn't 100% about.
Thanks for all your help gang!
Gx