@David Levi - Many Thanks for the full and detailed response, it has given me a lot to review and thanks for the link.
@Denver - Many Thanks, I am resident in Qatar and currently non resident in the UK for Tax, however the stone is a gift for my spouse. The reason the two stones are different is I wanted a bigger stone primarily, but the prices seemed out of range without large compromise on inclusions, the larger stone was not in the store but on zoomed 360 image from the dealer in Antwerp. Frankly speaking the store, which is called SHINE has quite a few stores in the middle east and I have had them recommended to me by people who have purchased here and then had them revalued (for retail and insurance purposes) in the UK and they seemed very happy. I honestly thought the tax thing would make a big difference than buying in the UK or EU where it would attract a VAT (i may be wrong on this as I've only just started researching).
For readers interest I confirm the Manager's last price for the 2.09 Carat was 45,8000 QAR / 3.64 = 12,582 USD including a white gold ring as a solitaire. He admitted the bigger stone was not as good quality and may have a slight milky appearance as untrained I couldn't see it on the screen.
On initial checks from different databases I have seen comparable that make it appear good value and others that were not so favorable. I will spend a lot more time reviewing the database David Levi sent through.
Thanks for the tips and advice - much appreciated.