Any experience with Serendipity Diamonds?

[BrainGrenades]

I came across some custom rings I liked by a jeweler called Serendipity Diamonds. They're in the UK but ship all over the world (I'm in the US). Has anyone ever purchased rings from this company and if so how would you rate the quality of the pieces? They do list "60 Days Returns" so I suppose that's an option if I really needed it. Another part to this question is what's the consensus on CanadaMark diamonds?

https://www.serendipitydiamonds.com/info/about-us