Think about it.
Your TV aerial points to a nearby TV transmitter, your dish points to a satelitte thousands of miles up in the sky.
BUT you can use an old Sky box and dish as a sort of freeview box (and get more channels).
Sky offer a freesat service where you pay them a one off payment of about �20 for a card which you put in a Sky box, and then you can pick up about 200 free channels.
There is no monthly payment, and the signal will probably be better than your freeview signal via an aerial.
See here
http://www.freesatfromsky.co.uk/
If you have already got the sky dish and sky box ignore the money figures on the home page, you just need to buy a Sky card for �20, see the FAQS on the site.