greywulff,
Stevekale beat me to it! As he says, there is no real difference in QUALITY between a Bronze and Gold cape - just QUANTITY of usable feathers.
Take a look here for more details as to how Whiting grade their capes/necks and saddles:
http://www.whitingfarms.com/articles/grading.html
I don't think that any UK retailer brings any Gold capes into the UK at the moment - mainly because the price is so prohibitive - they sell for £150 upwards as they are so rare.
There IS a difference between Whiting "red label" and "green label" capes - the Green Label re from the Hebert Miner gene pool - stiff barbs and excellent for traditional dry patterns - half the price of the Red Label which are from the Hoffman gene pool - supple stems and the barb count (number of barbs per inch of hackle stem) is about 50% higher so less wraps of hackle needed.
A Bronze grade cape will provide you with superb quality hackles, a revelation if you have only been tying with Indian capes.
If you wish to email me your full name and address, I will send you some samples of Whiting Red Label Dun hackles. I also have some superb deer that I have recently obtained from Northern Sweden - again, I can post you a sample.
Kind regards