Have your jewellery valued first. Then bring it along in person to one of these companies if they're in your local area. You'll find out there and then what they'll give you for your unwanted gold. Then, the decision is yours..... Do not post it to any company.
I did exactly as above and didn't work out too badly. The jewellery I had was unfashionable, broken chains, odd earings etc that were worth nothing to me lying around the house.
As I've said, attend in person following your own valuation and don't post anything.
Good luck!