Cheapest and safest way to send boxes from England to US?

Does anyone know of the best company to use for shipping boxes of our stuff back to the US from England?  I have used Royal Mail and had not so great experiences (I sent various handmade gift boxes to friends in US at Christmas, only to have 1/3 of them never arrive.)

I found out that DHL has the best prices (cheaper than Royal Mail and Fed Ex etc) and is an easy to use, secure way to send things without worry.

I used this company, sevenseasworldwide.com/, which was slow but worked just fine for shipping several boxes of books. It took a couple of months for them to arrive to the west coast of the US, but it worked well and nothing was damaged.