H Samuel have an 18ct yellow gold 1/2 carat diamond solitaire at half price, from 2K down to £999. Hope this helps.
that's a good price for that size of diamond. I'd show you the one i got for my missus but she might catch me looking at rings and think she's getting another one.
I got it from goldsmiths (canadian ice range) because it was the only one i could find that had a thin band, she's got tiny fingers so a standard thickness band looks a bit weird on her.