Well some channels can be watched abroad mainly news channels but the Iplayer etc all use location technology and are able to determine exactly where you are in the world based upon web technology using IP address and other information on your PC. You could at one time use a proxy server to overcome this problem but not any more I understand.
There are lots of websites such as _http://www.beelinetv.com/ but they will not give you your main channels I'm afraid
I am moving this post to terrestrial freeview section as it is not satellite based