Also make sure you check out Brastop.com:
http://www.brastop.com/
Yes the prices are in pounds, but don't worry they will take your credit card :) Also the exchange rate can be a killer, but Brastop regularly has bras on sale for like £10-15, which is about $30 and less than a bra of similar quality would cost here. Shipping is very reasonable too - a couple of years ago I bought a lady friend three Curvy Kate bras and with shipping it was less than $100, and when she had to exchange them for slightly larger sizes, the new ones cost a whopping $6.18 to ship. They're very good with returns and exchanges.
UK bra sizing IS a little different than U.S. sizing, so that's something to be aware of.
For fitting help, make sure you check out Bratabase:
http://www.bratabase.com/
and Invest in Your Chest:
http://www.investinyourchest.co.uk/