B_More,
There are four C's you should consider when getting your ring--cut, clarity, color, and carat. There are also different (unfortunately) rating certifications for rings, depending on how flawless they are. Mine has a high rating because it is absolutely flawless. I suspect the rating systems are different here from those in the States. Anyway, I'd still advise you to get your diamond from the States--you'll get twice as much of a ring than you would in the U.K. Also, you might get some good bargains online. I hope that helps.