Hi and thank you for the replies.
jrewing - The reason we had it valued, other than curiosity, was that I had heard that insurance companies would not accept a valuation document from the US and stating the value in dollars, and that we would have to have one in euros in order to get insured, although this might not be correct. I'll get onto insurance companies and see if they will accept the valuation in dollars.
NHG - As I'm not living in the same city as my parents I'm not sure I could put in on their contents insurance - in order to do so would I not need to state that I was living there? Maybe not, but I thought that if it was on their home insurance there would probably be some clause that the ring should be there most of the time, will look into it anyway thanks, and thanks for the congratulations!
01DMB - The website we got it from was diamonds-usa, they were very helpful. We were unlucky in that we did get caught for customs which was a bit of hassle but even so after paying the VAT and duty it cost a third of what it was valued at.
Thanks again for all the help.