I think any expert wuold need to handle it to make an assessment so I think you'll have to traipse. You might get a nice surprise though. What do you think it's made of? And does it say 'cartier, 'tiffany'' or 'faberge' anywhere on it That would be a hopeful sign!
I think it's gold. It was a 18th birthday present from a relative so probably not worth £1000s but £100s I guess. I feel terrible wanting to sell it but I don't like yellow gold, and have never worn it.