I used to have a jewelery manufacturing business, and last i heard there is a limit to how much gold you can actually own legally.
the exception is gold coins, as for it being a sound investment, i think not, the ass fell out of the gold market when they discovered gold in Russia, its now higher than its been for a long time, so IMHO you should sell sell sell.
as for scrap gold, its all relative, 9ct, 18ct 22 etc so buy accordingly. but remember only a manufacturer will pay you full rate or close to, jewelers and pawnbrokers will not give you anything close.
the best way to invest in gold is sovereign's, buy at scrap at present its about £95 a sovereign, when i was in the gold game around 2000 to 2002 it was £64 for a sovereign, thats why i say sell!
gold is not getting rarer as was suggested in this thread, its still being mined today, so my advice would be, sell your gold quick and get it in to domains
also gold does not alloy back when melted, if you take an ounce of scrap 9ct gold (clean) and melt it down and cast an ingot or chain then send it to be assayed, it will get a 9ct assay (hallmark)
and if you want to know what you should be paying for 9ct etc, devide the price by a troy ounce 31.1grm to get the 24ct per gram rate, then devide it by 24 and multiply it by 9 or 18 or whatever ct you want the price for, but remember, you need to buy below the quoted rate, at least 10% below, preferably 20.
door to door gold buyers:
Generally they are not looking for scrap as quoted in their leaflets, they are looking for broken repairable or vintage jewelery, if you do offer them total scrap they will give you less than half the going rate.
I used to sell Victorian and vintage jewelery mainly to America and one of my biggest sources was door to door guys, they used to get some real gems at ridiculously low prices.
also never buy new gold as an investment, you will blow your brains!
scrap gold on 9ct is probably around £5 a gram as we speak, jewelers sell for between £7 a gram for heavy stuff over an ounce from discount or market jewelers to £35 a gram from top high st jewelers