I'm not sure where you're flying from/to, or if this would be a possible option. But, if you can fly Continental instead of Virgin and if you have OnePass miles (or KLM Flying Dutchman Miles), it is possible to upgrade to First Class for 10,000 miles and a $300 (£150ish) change fee, which, if I'm reading the other posts correctly sounds a lot more economical in terms of both cash and miles. (Plus its actual first class, complete with table cloths and snooty flight attendants.
) I'm from Houston, which is Contintental's biggest hub or something, so this is the only airline I fly back to the States. I'm not sure what the others have to offer. I'm also not sure how much it costs if you have to pay. . .Just a thought. Either way, good luck!