Well, you can get some good technical data on what you need in order to receive Freeview properly at your home address by using the reception predictor located here:
http://www.wolfbane.com/cgi-bin/tvd.exe
Put your postcode into that and see what it tells you. It's helpful if you already know the name of your local transmitter and what direction it is from your house - that will enable you to spot it quickly from the list of transmitters shown in the results.
The result for your transmitter will tell you how far away it is (in miles), what its transmit power is and it will also state what sort of aerial you need. If you can run your postcode through the checker and then post back with the results, we can advise you further.
