It's apparently a myth that radio signals from ordinary
Earth radio and TV transmitters can be detected deep into
interstellar space. It seems rather that it doesn't even
penetrate a light year before getting drowned out by
background noise. Nonetheless, even a sphere six light
months in
radius is an enormous volume of space.
What might be happening, however, is that spacecraft may
be moving through that volume and detecting BBC
television. Nowadays it may be rather more difficult due
to it having gone digital, but I feel confident that a Phase
III civilisation is more than capable of hacking the signals
and turning them into passable video.
Let's do the maths.
Isaac Asimov's 'Extraterrestrial Civilisations' estimates that
there are 530 000 civilisations in the Milky Way.
Assuming the Milky Way to be a disc 50 000 light years in
radius and 3000 light years thick, and disregarding the
nucleus, diameter say 20 000 light years, as unsuitable for
life, we have a volume of very roughly 22 x 10^12 cubic
light years. This is an over-estimate.
Now suppose each planet has the same number of
interstellar flights as Earth has international airliner
flights. That's 37.4 million flights per planet per annum,
and of course the annum is different elsewhere and there
are hundreds of thousands of times the number of potential
destinations, so this is a huge underestimate too.
Hence it's not unreasonable to assume that there are over
20 x 10^12 interstellar journeys a year in this Galaxy.
Now divide the volume of the inhabited Galaxy as
calculated above by that of a sphere six light months in
diameter, which is around half a cubic light year. So that's
44 x 10^12 times the volume of the sphere in which it's
possible to receive BBC TV signals. That means that if
every alien craft is watching TV from nearby planets, it
ought to happen about once every two years, assuming the
distribution of flight paths through the Galaxy to be
random.
However, there could be hundreds or thousands of
passengers on board the offending starships, and not one of
them has a TV licence. What they probably do have,
though, is equipment capable of receiving TV signals.
Given that we have mobile phones even now, there will be
many of those aboard each starship. Therefore we only
need one such starship to pass through our local volume of
space to generate a reason to fine hundreds or thousands
of aliens.
So, my suggestion is to launch a fleet of TV detector
starships to patrol the space around the solar system and
pick up the signals from craft passing near us so the TV
Licencing Authority is motivated to make first contact with
spacefaring civilisations and fine them accordingly. These
fines can be used to finance the BBC space programme.