I've finally decided it's time to propose to my girlfriend. I don't have even the slightest doubt anymore that she's the person I want to spend the rest of my life with, so now I need to sort out the ring. I've never bought anything like this before and there seem to be endless choices once you start looking at stones, settings and metals. What sort of engagement rings are worth considering, what should I pay attention to, and where in the UK would you look for something genuinely beautiful?