If they are going as far as inspecting http traffic (and selectively editing/blocking some of it) with a transparently proxy rather than redirecting selected domains via DNS poisoning then your only way around this is some sort of VPN which of course requires a host elsewhere for the VPN server to run on (unless you use something like Tor, but that is very slow and may cause the same "many people from a small set of IP addresses" problem itself anyway due to the relatively limited number of exit nodes).