Absolutely - loads of companies (including the Royal Mint) sell them online. Prices seem to vary depending on whether the issue is collectable or not. If you're not fussed about buying something collectable but just want the best price, the mark-ups seem to be around 5% over the price of gold. Note that as well as not having to pay capital gains tax on profits, you don't pay any VAT [like a sales tax] on the sale either. This is very unusual - almost no other non-essential item is zero-rated for VAT.
