How is your PS3 connected to your PC (or MAC) - via wireless or wired to your (Virgin) router? In principle ISP / Virgin have no impact on the INTERNAL connection speed between your devices at home - only on your download / upload speeds from / to Internet.
Virgin cannot affect your Local speeds at all as its between your computer and your PS3 not using the internet at all. What might be a problem is that its connected through a router which slows it down. Try connecting it direct to your PC (or Mac) which will give the highest speeds possible but it will mean you'll have to do some networking. Follow the link GrandpaHomer has posted.