Jewelry Export requirements to European Union?

I make and sell handcrafted rings directly to customers in the US via
my wesite. On my receipts I include the description and composition
of precious metals used in the ring.

Will I have any difficulty selling (from a customs aspect) a single
ring directly (not for resale) to a customer in the UK? I know they
have strick requirements for assay. Or, since the ring will be
ordered directly off my US website, do only the US requirements apply?

Regards,
Ed Ferguson