Right, I measure at a 36" band, and my cup measurement is 48". BUT my boobs are odd. My left one is a couple of sizes smaller than my right one. This was very noticeable when I bent over to do the cup measurement. What size should I go for!?! Either way one boob will be lost or the other will be squished 
I have to shop online too as afaik there isn't anywhere close to me that does good fitting (I'm in Lincolnshire about half an hour away from Lincoln) :(