At the moment the Freeview signals are kept low so as to not interfere with the analogue signals.
Gradually, as analogue is turned off, the Freeview digital signals will be increased so you should be able to get them in future.
Note that the BBC and ITV are planning to bring out a free satellite service soon called Freesat which will be in high definition (HD).
I do not know too much about it, but I believe it will come through a dish (which could be your old sky dish) but you will need a new "box".
After you have bought the box there is no monthly charge.
More here:
http://www.freesat.co.uk/home.php