I used to do a lot of jewelry shopping in HK until I realize that the chain stuff is all a lot cheaper in the USA. Again, not sure about the small boutiques, but I know that Chow Tai Fook and CSS are everywhere and reliable. I'm not sure if they have a store in HK, but middle-class Chinese like 'Enzo' a lot - it's a division of LJ Diamonds. They also like Cartier (naturally), but their stuff is $$$$$. I feel like you can get more bang for your buck at the chain stores and your wife will definitely appreciate that.
I'm not sure at all of the UK pricing, but it always irritates me seeing prices that are a lot higher than they are at home (USA) - especially when I'm going to spend a lot of cash. A way to check to see the general pricing difference is to look at the prices at a major chain like Tiffany's or Cartier, and compare with the price at home. I'll look and compare and see if it's worth the time waiting until the next trip home to buy something.