If you're not in the UK then you won't be able to watch any of the domestic UK television channels online. This is because they are restricted to those people who are in the United Kingdom.
Fortunately there is a way to bypass this restriction by setting up a UK VPN to hide your location. This works because sites like the BBC check your IP address when you connect to their site. They then look up the location of that address and either block or allow access.
If you connect using a UK based VPN server then your real address is hidden and the site only see the UK address of the server. This will instantly allow you access to all UK TV sites.
Watch this video for a quick demonstration of how easy it is.