Hi,
I found a little program called Proxy Changer that makes it simple to switch between proxys..
http://www.proxychanger.com/
You basically add proxies and then it lets you swap between them at the click of a button. The list of added proxies is stored in an INI file in the Windows directory.
Attached is a TXT file I've prepared that, if renamed as an INI file and copied over the one in your Windows directory, will populate proxychanger with all NTLs current proxy caches via port 8080.
All you need do is download and install this little tool (314Kb) then replace the INI file and you'll then be able to hot-swap between proxies.
Hopefully this will be a useful tool for all those (like me) who are forever having proxy issues.
-EvilRix