Freeserve/Wanadoo no longer use proxies, they did away with them while I was still with them a year or so ago - Eusa would probably know more about that.
Virgin uses NTL's network I believe ?
AOL certainly does use proxies, but doesn't seem to suffer the same non site loading as NTL does.
Proxies are a pain in the bum, not a day goes by when I don't have to change proxies manually to get a certain site to load
cheers
Ian