If you've just signed up, then you don't have the "thinking of leaving us" option.
So it's either:
1. Add TV with VM (on bundle builder, its actually dearer with 50 than 100)
2. Get a freeview antenna, try Wolfbane for an idea of what you'd need.
http://www.wolfbane.net/cgi-bin/tvd.exe?
"Log periodic" I think is the minimum antenna suggestion, I get that and can achieve adequate results with a set-top antenna.
3. Consider installing a Freesat system - some channels that are not on freeview, but some channels missing that are on freeview - possibly some extra FTA channels that can be added but are not indexed by the EPG