It will make your life much easier to only consider stones that score under 2 on the HCA. You can use the PS search tool and put in about 5K USD as your budget. Only consider stones that score "Excellent" on the HCA, and you can sort by vendor to only consider stones from BN. When you click on a given stone, currency will be in USD, so you have to change it to "shipping to UK" in order to see price in sterling.These are the 7 i am trying to select from https://www.bluenile.com/uk/diamond-search?track=all