You can always go to
http://www.traveljungle.co.uk. There you can list any start airport/city. I fly on United sometimes and you can do this on their site
http://www.unitedairlines.co.uk.
I've found that the biggest savings can be made over bank holidays in the Uk. It's always cheaper to book from continental Europe. You also find that BA fares are always cheaper from continental Europe. Their club fares from Italy to America/ Asia are very cheap at the moment.
I'm not sure how this would work for Virgin though. IT would obvioulsy mean flying to Continental Europe and then back again before flying on VS