When I am using my Virgin Media broadband (either wireless or wired) any downloads from Apple Inc. services are extremely slow (such as downloads from the AppStore, iCloud.com and developer.apple.com).
All other sites are unaffected. And it doesn't seem to be a problem on Apple's side, as other people I know don't have this problem.
I am sorry you are having problems with slow downloads from Apple, I have just tested your connection and as you mentioned it all looks good. It may be worth trying a traceroute to Apple as it may reveal something, if that looks good then perhaps contact Apple support as it may be server bandwidth etc.