TV signals are transmitted in two ways. The traditional way is the transmission over air where you use an external antenna to catch the signals. Here the signals are scattered across the atmosphere and have limited range usually 25 to 50 KM. To extend their reach, broadcasting companies use relays (or repeaters) of transmitters that cover a wider geographical area. To save energy, most broadcasting companies use LPTs or Low Powered Transmitters. That is the reason why the transmission are usually available to a max of about 50 Km around the position of the transmitter's antenna. Such transmission are usually free and is done by government owned broadcasters such as AIR, BBC. etc.
The only way to reach across the world is through satellites. Each broadcaster beams his signal(s) to a satellite that is stationery above his head. This satellite, if necessary amplifies the signals, and then beams the signals back to the earth covering a much larger area. You need a special receiver and a dish (antenna) that is pointed at the satellite. A few years ago, this was an expensive proposition and you had cable operators who would receive the signals using large arrays of antennas, re-amplify the signals, and send them to your house through cables.
Today the technology has reached a level where you can receive the signals yourself using a small dish on your rooftop.
These satellites are usually geo-stationary. In other words they are rotating at the same speed as the earth so they seem to be hovering over your head all the time. These satellites also exchange data for worldwide transmission. For example, a satellite over San Francisco can transmit Indian channels such as Star or Sun. This is done by hopping the signals across multiple satellites in the sky till it reaches the satellite that is geostationary over SFO.
For the BBC signals to reach you, the satellite over UK must hop the signals to a satellite that is stationary over India. This would need an agreement between the two companies managing the satellites. Check with your DTH provider and see if he can include BBC signals as part of the package you receive. You get Discovery, HBO, and other channels this way.
Other than this (leaving aside the NET, of course) there is no way you can receive BBC signals on your TV in India. Unless you have the technology and smartness to hack into a satellite's signals.