Try this one first - cache6-lutn.server.ntli.net IP = 62.252.64.9 port 8080
If that does not work then I find that the watford ones work well most of the time.
This one - cache2-wtfd.server.ntli.net 80.3.0.42 port 8080 usualy works well...
It sounds like you may be stuck on the luton 1 cache...
Go here -
www.all-nettools.com and click on proxy test... This will tell you the proxy you are currently on...
HTH