We thought about making our rings there but decided not to in the end. Neither of us were completely comfortable with the idea of working with molten metal and we knew that we'd never get it looking perfect (we have slightly perfectionist tendencies

)I ended up getting my ring from Bernstone's on Hatton Garden and they modified an existing design to my requirements.
It is a really romantic concept though, and it always gets rave reviews from those who have been there and done it.
Forgot to say - there are loads of manufacturing jewellers and designers on Hatton Garden. Most of the designers don't have websites and work on word of mouth which is a bit of a pain but if they're good then there are usually enthusiastic posts on wedding guide etc