With digital TV, several programs are transmitted on the same channel.
Check out this website:
http://www.wolfbane.com/cgi-bin/tvd.exe?DX=L&HT=10&OS=me10+2qs
You would probably be best using the Bluebell Hill transmitter, but it depends whether there's a good line of sight form where you are.
Some channels are transmitted at a lower power or are more prone to interference than others, so your box may not receive some of the more difficult channels.
Check out if the channels you can't get are all in the same group(s) at this site:
http://www.unsatisfactorysoftware.co.uk/dtt/dtt.cgi
As the earlier answer says, there's no such thing as a "digital aerial", but it is good to get the right aerial for the channels used by your transmitter.
Use an outside aerial (you can loose 6dB of signal [half] just going throiugh a roof)
Use a decent, fully screened cable as well, not the cheapo co-ax that was so popular in the past.
Have the aerial as high as you sensibly can
Keep it away fro other aerials and metalwork.
Check out
http://www.satcure.co.uk/tech/freeview_problems.htm
as well.
John
February 2008