I've always been a huge fan of
H&M Bras since I discovered them on a trip to Germany years ago. They are equivalent in quality to anything you'd find at Victoria's Secret, La Senza or similar stores, they fit amazingly well, and best of all, are a fraction of the price you'd find anywhere else.
They also come in hard to find sizes like 32 B, C, etc - which I can rarely find anywhere...