I would ring a refiner and ask what the minimum is and check the cost of the service - that should give you a clue.
Re. jewelery - imo - if I wanted to get rid of some gold right now and I had a choice between bullion/coins/jewelery - I would actually keep the jewelery - why?
Because jewelery is the last form of gold to be confiscated. Also, it is the hardest to sell and get max value from - unless you are only wanting to get the metal value from it - in which case you are back to your original problem.
I would have thought if one wanted to make a quid - the way to go would be to set up as a gold buyer - if the prices you talked about are an indication of the margins they would be making :)
