If you have a scan through the forums you find people listing good and bad suppliers. Most companies will have a few negative comments on them, but this doesn't necessarily make them a bad supplier. One way of checking the buying experience from a company would be to buy a low value item from a company, and see how you fare.
Personally I have ordered from the following companies and can generally report positive experiences. click here click here click here click here click here
I personally found click here a real pain, but I'm sure other people will recommend them.
I found these guys click here very speedy delivery, slightly hard to get hold off but refund very quickly if necessary
For price comparison try click here click here click here and click here
Hope this is of some help