Shipping from the UK can be pricey. Royal Mail is expensive.
I just had a couple of packages sent from the UK, probably a bit larger and heavier than a typical body protector @ 11 lbs (5 kg). They cost me 60 pounds (about US$100) for shipping.
I like the look of the Airowear Outlyne protectors myself. After the safety issues (discussed above) I think the most important issue is fit. So you have to look at the shape of the protector, as well as the size. Too tight means it will be too hot, but if its too big, it will bump on your cantle and interfere with movement.
I would study the size charts for the models you are considering, and try to choose one that matches your proportions. The measurements they use are your bust, waist, and distance from waist to waist over your shoulder. This link should be helpful for fitting:
BETA Safety - Fitting Body Protectors
And this link helps to explain more about the difference between BETA:2000 and BETA:2009