Trying to get a Diamond engagement ring!?

I have come accross the following website
www.londonantwerpdiamonds.com – who are diamond brokers in Canary wharf and office in Antwerp. They say the prices are the same to buy a diamond in Canary wharf as to go to antwerp to buy the diamond.
Can anyone advise?
Also is hatton garden the best place to get diamond engagement rings?
And has anyone any experience with Diamond workshop in Hatton Garden.
Any diamond I get I will be getting a certificate.

There are lovely rings here -

http://www.chapelle.co.uk/Diamond-Rings/Solitaire/Gold/?price=500

Canary Diamond Engagement
Canary Diamond Engagement
Canary Diamond Engagement