I bought Mrs Globalste's engagement ring and wedding ring from Daniel Prince at Hatton Garden.

I asked him to make a Tiffany Novo style ring with a 1ct diamond and 18diamonds around the shoulder. The quality of the work was outstanding and the price was about 30% less than Tiffanys. I then got him to make the wedding ring which is chamfered to fit around the main diamond in the engagement ring and also has . There are pics of it on his site i think.

I would highly recommend him if you are considering purchasing from the UK.

http://www.danielprince.co.uk/

Best thing to do about ring sizing is get a ring measuring stick off ebay for £5 then measure one of her rings she wears. If she doesnt wear it then it could be tough to guess, as mentioned above, ring sizing is redone using a laser where they cut the ring and re-join it, so therefore they can only adjust by a couple of sizes.